how to identify which form's button is clicked- still not cleared

Question

Hi,

I have three forms form1, form2, and form3. In form1 I have a button and datagridview. The button on clicking takes control into form3. Similarly in form2 also I have a button and a dgv. The button on click takes control to form3. Now in form3 I want to identify which forms button is pressed. I mean if I have clicked form1's button then I will access form1's dgv or if I have clicked form2's button then I will access form2's dgv. How to know which form's button I have clicked in form3?

thanks