Query Builder

[Charlie]

I am working on a form with a combo box displaying supplier codes, I want to add a text box next to this showing the suppliers name.
I have been advised to do this in a certain way which is, select the form, on the menu bar select edit (I havent a clue what that is)then click on the record source property in the properties window.
next im supposed to click the build button to start the query builder.
I am lost can someone fathom what this means, and advise me what to do here please.

Charlie

 

[Charlie]

what i am trying to do is place a text box next to my supplier code combo box linking the two so that when a code is selected the relevant name is displayed in the text box.When I try to do it I get an error, If I link another field it is ok though, I just wonder what is causing this error?
http://homepage.ntlworld.com/charlie_chuck/Invoice09.mdb

The problem is with the frmInvoice1

Cheers Charlie