Macro sc_time_diff

Hello, I am new to SC9, I have to calculate a difference between 2 hours and that I can see it on the screen and save it to the base, I am trying with sc_time_diff but it does not show me the formatted result. Eg if the difference is 9:10 it saves me 91:00. Like to enter the time I have to put 09:00 always a 0 ahead.
Thank you.