How to Enable Disable Required Field Validator using JavaScript

 function autoSelect()
{   
var DelRecvName = document.getElementById("TxtDelRecvName").value;  
  if (DelRecvName == "")   
    { 
    ValidatorEnable(document.getElementById("RequiredFieldValidator3"), false);                          ValidatorEnable(document.getElementById("RequiredFieldValidator10"), false);         ValidatorEnable(document.getElementById("RequiredFieldValidator13"), false);         ValidatorEnable(document.getElementById("RequiredFieldValidator14"), false);        }       
else    
   {       
 ValidatorEnable(document.getElementById("RequiredFieldValidator3"), true);         ValidatorEnable(document.getElementById("RequiredFieldValidator10"), true);         ValidatorEnable(document.getElementById("RequiredFieldValidator13"), true);         ValidatorEnable(document.getElementById("RequiredFieldValidator14"), true); 
      } 
}