[AccessD] Unbound subform

I have a form that contains a subform.  I would like
this subform to be unbound and not visible until a
button is clicked on the main form. I cannot get the
subform bound properly.  I get the "The expression you
entered refers to an object that is closed or doesn't
exist" error.
I had it at one time and lost it.
Any ideas?
TIA
Nancy


The name of the subform control is sbffrmReceiving
The name of the subform is frmReceiving
I put the name of the subform control it the control's
tag property.

This is the code I am using:
Private sub cmdOpenRec_Click():

Me.sbffrmReceiving.Visible = True
Me.sbffrmReceiving.SetFocus

If Len(Me.sbffrmReceiving.Form.SourceObject) = 0 Then

Me.sbffrmReceiving.Form.SourceObject =
Me.sbffrmReceiving.Form.Tag
               
Me.sbffrmReceiving.Form.LinkChildFields =
Forms!Me.sbffrmReceiving.Form.LinkChildFields
               
Me.sbffrmReceiving.Form.LinkMasterFields =
Me.sbffrmReceiving.Form.LinkMasterFields
 End If