hi,
i am creating a sub form which i need to open when the answer in one of my field is yes. once that yes is clicked i would like the subform to open. help!

Se the Visible property of the subform to NO.
On the after Update Event of the check box put...

If CheckBoxName=True Then
SubformName.Visible = True
Else
SubformName.Visible = False
End If

HTH