How to trak button content?

Hi Expert!,

                  in step loop i have created 6 buttons and i'm printing PO  number on the button insted of button text(Purchase order is printed as text label).Now i have been asked to retrieve the PO from selected button. I'm unable to retrieve value(PO number),where as if i would have taken input output field, I could retrieve PO number  easily through GET and Set CURSOR.

button b1      0000000045 (on button as text in step loop)

button b2      0000000046

button b3      0000000047

Now please help me out .

Thanks In Advance.