How to add a variable token to an iExpense approver notification?

Hi,

  I wanted to add the preparer name to the email notification that the approver receives.  So, I added the token &PREPARER_NAME in the body of message OIE_REQ_EXP_REP_APPR_INST.   However, when the email notification is received, it doesn't substitute the value, it just displays the variable token &PREPARER_NAME.   Is there some other step that I've missed?  Do I need to customize the workflow to get that value to be set.  I thought it was standard one that would already be set.