Set CRM 2011 field requirement level in runtime

CRM 2011 

// No Constraint
Xrm.Page.getAttribute("field_schema_name").setRequiredLevel("none");
 
// Business Required
Xrm.Page.getAttribute("field_schema_name").setRequiredLevel("required");
 
// Business Recommended
Xrm.Page.getAttribute("field_schema_name").setRequiredLevel("recommended");

CRM 4.0 



// No Constraint
crmForm.SetFieldReqLevel("field_schema_name", 0);
 
// Business Required
crmForm.SetFieldReqLevel("field_schema_name", 1);
 
// Business Recommended
crmForm.SetFieldReqLevel("field_schema_name", 2);