One of the most common mistakes I see, and hear about it, is improper syntax when referencing controls on a subform. As far as Access is concerned, a subform is just another control on the main form — and that’s what confuses folks.

First, let’s review referencing controls in general. Use either of the following syntax statements to reference a control on a main form:

Forms!formname!controlname

Me!controlname

(In more recent versions, you can substitute bang (!) with dot (.) between objects.)

To refer to a subform or a control on a subform, you must remember that Access treats the subform as a control. Essentially, you have a form with a control with a control. To express that arrangement in terms Access can decipher, you need the Form property as follows

Forms!mainform!subform.Form.controlonsubform

Me!subform.Form.controlonsubform

In other words, subform is simply a control on the main form.

What I commonly see is a simple transposition of the Form property and subform, which generates a runtime error:

Forms!mainform.Form.subform.controlonsubform

In this form, Access assumes Form is a control. When it can’t find a control named form, Access returns an error.