Timestamp when you hit the 'Print' Button

I have very limited knowledge and experience using LiveCycle Design and Javascript/XML.  I have added a print button to my form but I would like the timestamp to go into a text box (printtimestamp) before the form prints.  I am not sure what the code is that I should use or where to put that code in the print button.  Please help me with the code and where to put it. 

AceBK