Newbie - Replace blank fields with "Customer"

[Ady]

Hi There

I am doing a mailmerge from excel to word. In one of the word fields will be
the customer name. However some fields within the excel columns will be
blank.

I need to achieve the following:
In the contact field, If the field in the database is blank it needs to
insert "Customer".

I am a newbie so could you please make your answers in plain English!!!

Many thanks for your help.

Ady