How do I reference the current form in an expression in Microsoft Access?

You can use:

=MyFunction([Form])

The code would be:

Function MyFunction(frm As Form)
MsgBox frm.Name
End Function

'me' can only be called from within the corresponding form object (ie in the object's procedures, functions and events).

My favorite way to refer to the current form is to call the screen.activeForm object...

screen.activeForm.recordset.fields(myFieldname).value
screen.activeForm.controls(myControl).value
screen.activeForm.name
....

Of course you can send the form object to a custom function

my Result = myCustomFunction(screen.activeForm)

Or you could build a user-defined object. The needed fields could then be considered as internal properties, set in the Class_Initialize sub of the corresponding object.

If you are using code in the form, then "me" referrers to the current form. So

Call SomeFunction(me)

However, "me" can't be used in the context of a expression that is bound to a text box.

In that case you can either pick up the current screen in the routine with screen.activeform as suggested.

I often go:

Dim f     as form
Set f = screen.ActiveForm