Joining fields / concatenating

Joining fields / concatenating

Hi - I have a Product Master form and a Products form.

A Product Master can have more then 1 Product - so a Master could be "brown wrapping paper" with a Code of "BWP" and the Product could be "900mm wide" with a Code of "900MM".

So I want to allow the user to select a Product Master from a look up list - I know how to do this - and then enter the Code "900MM" and have the Product show the result as "BWP-900MM"

I have looked through the help and can't see how to concatenate / join those 2 fields...

It is probably simple...

Thank you