function DoSomething()
{
// Define the role names you wish to allow
var allowedRoles = [ "Planer", "Systemadministrator" ];
    
// Check to see if the user's role matches one of the defined allowed roles
var roleAllowed = IsRoleAllowed(allowedRoles);

// If the role is not allowed, then alert
 if (! roleAllowed)
 {
  alert('Sie sind nicht berechtigt, die Funktion auszuführen.'
  return;
 }
  
// Here comes the code which should fire, if the user is allowed
   
}

function IsRoleAllowed(allowedRoles)
{
  // Find the user security roles
  var result = RetrieveUserRoles();
  var foundResult = false;
 
  // Loop through the allowed role list checking if the user belongs to one of the roles.
  for (i=0;i<=allowedRoles.length;i++)
  {
    if (result.indexOf(allowedRoles[i]) > -1 )
    {
      foundResult = true;
      break;
    }
  }
 
  return foundResult;
}

// Method to return the user's security roles
function RetrieveUserRoles()
{
  // Define URL to CRM API service
  var serverUrl = "/mscrmservices/2007/crmservice.asmx";

  // Set up XMLHTTP request
  var xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
  xmlhttp.open("POST", serverUrl, false);
  xmlhttp.setRequestHeader("Content-Type", "text/xml; charset=utf-8")

  // Specify correct SOAP action in the header
  xmlhttp.setRequestHeader("SOAPAction", "http://schemas.microsoft.com/crm/2007/WebServices/RetrieveMultiple")

// Define the retrievemultiple message
  var message =
  [
    "<?xml version='1.0' encoding='utf-8'?>",
    "<soap:Envelope xmlns:soap=\"http://schemas.xmlsoap.org/soap/envelope/\" xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\">",
    "<soap:Header>",
    "<CrmAuthenticationToken  xmlns=\"http://schemas.microsoft.com/crm/2007/WebServices\">",
 "<AuthenticationType xmlns=\"http://schemas.microsoft.com/crm/2007/CoreTypes\">0</AuthenticationType>",
 // Change Microsoft for your Organization name here.
 "<OrganizationName  xmlns=\"http://schemas.microsoft.com/crm/2007/CoreTypes\">MicrosoftCRM</OrganizationName>",
 "<CallerId xmlns=\"http://schemas.microsoft.com/crm/2007/CoreTypes\">00000000-0000-0000-0000-000000000000</CallerId>",
 "</CrmAuthenticationToken>",
 "</soap:Header>",
    "<soap:Body>",
    "<RetrieveMultiple xmlns='http://schemas.microsoft.com/crm/2007/WebServices'>",
    "<query xmlns:q1='http://schemas.microsoft.com/crm/2006/Query' xsi:type='q1:QueryExpression'>",
    "<q1:EntityName>role</q1:EntityName>",
    "<q1:ColumnSet xsi:type='q1:ColumnSet'><q1:Attributes><q1:Attribute>name</q1:Attribute></q1:Attributes></q1:ColumnSet>",
    "<q1:Distinct>false</q1:Distinct>",
    "<q1:LinkEntities>",
    "<q1:LinkEntity>",
    "<q1:LinkFromAttributeName>roleid</q1:LinkFromAttributeName>",
    "<q1:LinkFromEntityName>role</q1:LinkFromEntityName>",
    "<q1:LinkToEntityName>systemuserroles</q1:LinkToEntityName>",
    "<q1:LinkToAttributeName>roleid</q1:LinkToAttributeName>",
    "<q1:JoinOperator>Inner</q1:JoinOperator>",
    "<q1:LinkEntities>",
    "<q1:LinkEntity>",
    "<q1:LinkFromAttributeName>systemuserid</q1:LinkFromAttributeName>",
    "<q1:LinkFromEntityName>systemuserroles</q1:LinkFromEntityName>",
    "<q1:LinkToEntityName>systemuser</q1:LinkToEntityName>",
    "<q1:LinkToAttributeName>systemuserid</q1:LinkToAttributeName>",
    "<q1:JoinOperator>Inner</q1:JoinOperator>",
    "<q1:LinkCriteria>",
    "<q1:FilterOperator>And</q1:FilterOperator>",
    "<q1:Conditions>",
    "<q1:Condition>",
    "<q1:AttributeName>systemuserid</q1:AttributeName>",
    "<q1:Operator>Equal</q1:Operator>",
    "<q1:Values>",
    "<q1:Value xmlns:q2='http://microsoft.com/wsdl/types/' xsi:type='q2:guid'>",
    GetUserId(),
    "</q1:Value>",
    "</q1:Values>",
    "</q1:Condition>",
    "</q1:Conditions>",
    "</q1:LinkCriteria>",
    "</q1:LinkEntity>",
    "</q1:LinkEntities>",
    "</q1:LinkEntity>",
    "</q1:LinkEntities>",
    "</query>",
    "</RetrieveMultiple>",
    "</soap:Body>",
    "</soap:Envelope>"
  ].join("");

// Submit to the CRM API web service and receive a response
  xmlhttp.send(message);
  return xmlhttp.responseXML.text;
}

// Method to return the current user's systemuserid
function GetUserId()
{
  // Define URL to CRM API service
  var serverUrl = "/mscrmservices/2007/crmservice.asmx";

  // Set up XMLHTTP request
  var xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
  xmlhttp.open("POST", serverUrl, false);
  xmlhttp.setRequestHeader("Content-Type", "text/xml; charset=utf-8")

  // Specify correct SOAP action in the header
  xmlhttp.setRequestHeader("SOAPAction", "http://schemas.microsoft.com/crm/2007/WebServices/Execute")

// Define the execute message
  var message =
  [
    "<?xml version='1.0' encoding='utf-8'?>",
    "<soap:Envelope xmlns:soap=\"http://schemas.xmlsoap.org/soap/envelope/\" xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\">",
    "<soap:Header>",
    "<CrmAuthenticationToken  xmlns=\"http://schemas.microsoft.com/crm/2007/WebServices\">",
 "<AuthenticationType xmlns=\"http://schemas.microsoft.com/crm/2007/CoreTypes\">0</AuthenticationType>",
 // Change MicrosoftCRM for your Organization name here.
 "<OrganizationName  xmlns=\"http://schemas.microsoft.com/crm/2007/CoreTypes\">MicrosoftCRM</OrganizationName>",
 "<CallerId xmlns=\"http://schemas.microsoft.com/crm/2007/CoreTypes\">00000000-0000-0000-0000-000000000000</CallerId>",
 "</CrmAuthenticationToken>",
 "</soap:Header>",
    "<soap:Body>",
    "<Execute xmlns='http://schemas.microsoft.com/crm/2007/WebServices'>",
    "<Request xsi:type='WhoAmIRequest' />",
    "</Execute>",
    "</soap:Body>",
    "</soap:Envelope>"
  ].join("");

// Submit to the CRM API web service and receive a response
  xmlhttp.send(message);
  var result = xmlhttp.responseXML.xml;

// Create a new DOM document and load the response XML
  var doc = new ActiveXObject("MSXML2.DOMDocument");
  doc.async = false;
  doc.loadXML(result);

  // Return the userid node

  var returnNode = doc.selectSingleNode("//UserId");
  if( returnNode != null )
  {
    // If the userid node exists, return its value
    return returnNode.text;
  }
  else
  {
    return null;
  }
}