Error in displaying User full name for Requirement's

Hi All, 

I am trying to display user full name in requirement module for author field. I am trying the below code

Sub Req_New

Set reqList = TDConnection.ReqFactory.NewList("")
For Each rq in reqList
if rq.Field("RQ_USER_04") = "" then
rq.Field("RQ_USER_04") = TDConnection.Customization.Users.User(rq.Field("RQ_REQ_AUTHOR")).FullName
rq.Post
end if
Next

On Error GoTo 0
End Sub

Somehow the code doesn't work .  when new requirement is created full name is displayed but some times when I create a new requirement in Requirements Detail view full name is not displayed. Is there any thing wrong with the code please let me know. 

We are using HP ALM 11 Patch 7