CRM 4.0 : Error about script HideTab,HideField

Hi,

I got error about script for HideTab,HideField by security Role details

Role : Sales Person
Field : productid
Tab: 2 from left to right (It is correct ?)
Input to OnLoad as details;

var UserRoles = GetCurrentUserRoles(); 
HideTabByRole("Sales person" , UserRoles, 2);  
HideFieldByRole('Sales person', UserRoles, 
  crmForm.all.productid, 
  crmForm.all.productid_c,  
  crmForm.all.productid_d); 

The error i got as details

Field:window
Event:onload
Error : The value of the property 'GetCurrentUserRoles' is null or undefined, not a Function object

Please help and suggestion. Thank you