Using Merge Field in file name?

Hi All,

I'm trying to put together a simple bit of code that cycles through my mail merge, and prints to PDF using a merge field value as a file name. The code i've got at the minute is as follows:

Sub letter()
'
Dim ghName As String

ghName = ** This is where I want to use a merge field **


Do


    ActiveDocument.MailMerge.DataSource.ActiveRecord = wdNextRecord
    
    ActiveDocument.PrintOut
** This is where I want to set the documents name to the merge field value & "letter"**
   
Loop


End Sub

I'm normally fairly competant in excel with this sort of thing but word is a new ball game for me so any help would be much appreciated