Passing variables from forms

[Adam Pedder]

I've upsized a database and am having a problem with subforms that take a
parameter from a form.

I've followed the instructions in Upsizing Tools documentation and created a
function that accepts a parameter and that test out fine.

I've then set the record source as

Select * From datefunction(@Forms!NewDeal!ID)

and the input parameters as ? = Forms!NewDeal!ID

My problem is that when I open the form I get the error: "Must declare the
variable 'Forms'"

How do I declare Forms?

Thanks,

Adam