ok ... I get what you are trying to do.
1) Is the ID field displaying on the sub form ? If so, give that text box a Name of txtID ... then change the code as shown below
2) Is the ID field Numeric ? Or Text ?
Private Sub Form_Current()
Me.Parent.Form.Filter = "[ID] = " & Me.txtID ' If ID is Numeric
' Me.Parent.Form.Filter = "[ID] = " & Chr(34) & Me.txtID & Chr(34) ' If ID is text
Me.Parent.Form.FilterOn = True
End Sub
mx