Not sure I agree that the Command1_Click() event helps as written since it sets the value of a control or field to be the value chosen from the combo.
Lot's of ways to do this, I think. Simplest might be to have a hidden unbound text box on the first form. Set its value according to the button that was clicked on the dialog form. When the dialog closes, execution returns to the first form, where you test the value. You shouldn't have to requery the textbox, but watch for that.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.