Using Parent is the proper syntax.
Open your form in design view.
Click on the where the sub form is.
It will be a subform control. The subform has a name like any other object.
It may or may not be the same name as the form being used as the subform.
The Source Object property of the subform control contains the name of the
form that is attached as a subform.
So there are two names, one for the subform control and one for the subform.
They can (but to avoid confusion, should not be) the same.
In your code you want to refer to the name of the subform control. So the
correct syntax is
Me.Parent![SubFormControl1].Form![ControlName].Value
Me.... references the active form
Parent... The main form
SubFormControl1... The name of the subform control on the main form.
Form... refers to the subform control source object
ControlName... The name of the control on the subform control's form.
Value is optional, you don't really need it. It is the default property.
Does SubFormControl1 refer to to SubForm1? Could you give the syntax without
using the parent ?
I am a little confused on what you were trying to say!