how to get datagridview value from one form to another form

Question

hai i have 2 forms form1 has textbox,button-(when i click on this button it redirects to form2 which has a datagridview and button(btnok))and when i double click on cell or click on btnok(button) of datagridview i want to get data of that cell value into form1 textbox(txtpubcode).