If you have ever tried to build an application in MS Access you probably came across the problem of referring to a control from a main form to its sub-form. Here is a very brief guide how should the reference look like.

A complete reference should be as follows:

Forms![FormName]![SubFormName].Form![ControlName]
or Form_FormName![SubFormName].Form![ControlName]
or Forms("FormName")![SubFormName].Form![ControlName]

FormName stands for the name of the main form.
SubFormName is the name of the sub-form.
ControlName is the name of the control (text box, label, check box etc.) that you want to refer to

If you want to use a shorter version then you can use the internal reference. The reference will look like this:

Me![SubFormName].Form![ControlName]

It is referencing a sub-form from the opened form (“Me” ).