Dave your post is a little vague so I'll give you a general answer
If you try to reference subforms form your main form in VBA the use the syntax -
[Forms]![your main form name]![you subform name].Form
or
Me![your subforms name].Form
This will allow you to make changes to subform properties i.e AllowEdits, Enabled etc
e.g Me![you subform name].Form.Visible = True
Are you getting any VBA error messages?