Nathan,
Yeah, this is a good little trick you're onto. Anthony's answer on how to reference the other subform is correct, but depending on what you're trying to do, may not be necessary. In general, the way to refer to a subform is:
forms!NameOfMainForm!NameOfControlThatHoldsSubform.form
and from there you tack on either:
.NameOfPropertyOfTheSubform
or
!NameOfControlOnTheSubform
But if what you've got going on is two subforms on the same form, and you want the rows of subform2 to be keyed to the record selected in subform1, you can do without that.
I have a form that tracks Accounts. There's one subform that holds Discrepancies found in the account and one subform that lists who received e-mails about the discrepancy that's selected in the first subform.
Making it work is rather simple. In the first subform's OnCurrent event I have a single line of code:
Me.Parent!txtDiscrepancyID = Me!txtDiscrepancyID
This sets an invisible control on the main form to the Primary Key value of the stuff in the first subform. The second subform has it's Link Master Field set to that control on the main form. This means that every time I change records in the first subform, the records in the second subform are updated to be relevant to the newly selected record in that first subform.
If that's what you're trying to do, you won't have to refer to the second subform at all. But I'm just guessing that that's what you're trying to do.
Hope this helps.
Jeremy =============
Jeremy Wallace
AlphaBet City Dataworks
Take a look at the Developers' section of the site for some helpful fundamentals.