Question : When trying to use a subform, I am getting an error that says a link cannot be created to an unbound form.

I have a form and a subform. I am trying to relate the two based on a common field. When I try, I get the " a link cannot be created to an unbound form" error.

Apparently I don't know what an unbound form is. This form is opened by another form which provides it the record number to which it should open. I am assuming that is the problem, but I don't see a way around it.

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Answer : When trying to use a subform, I am getting an error that says a link cannot be created to an unbound form.

[19|20] means any character: 1, 9, 2, or 0 -- the vertical bar is redundant. The plus means one or more of the previous, so one or more of 1, 9, 2, or 0. The rest means exactly two numeric digits.

Try the following pattern instead:

1:	(19|20)\d{2}