CANCEL like cancel selected value

[eugz]

Hi All.
Form1 has ComboBox1 and 2 buttons: OK and CANCEL. When user selected value in ComboBox1 and pressed OK preview report will open. I would like when user click CANCEL value in ComboBox1 will canceled but Form1 will not closed. How to do it?
Thanks.

 

[RuralGuy]

Me.ComboBox1 = Null