Please help

[Dave B]

Could any body please help with the following problem,

I am trying use Dlookup on the after update event of a
text box (called Part Name) to return
The ‘Part ID’ of a ‘Part’ from the ‘Parts Table’ based on
on the following (help file code).
Dlookup ("[Part ID]", "Parts", "[Part Name] = " & Forms!
Part list! Part Name)
Each time I update the text box I get the following error
message,
Run time error 2471 the object doesn’t contain the
automation object & Part Name.

Part ID: is an indexed (no duplicates) auto number field.
Part Name: is an indexed (no Duplicates) text field.

Any help would be most appricated.