Gettting thelast page of gravity multipage form

I 'm looking for a function allowing to calculate the number of page generated by multipage form in GravityForm

I know there is this function $current_page = rgpost( 'gform_source_page_number_' . $form['id'] ) ? rgpost( 'gform_source_page_number_' . $form['id'] ) : 1; but i would like a function to get the number of the last page too

because i need the number od the first and the last page. thanks a lot

via Chebli Mohamed