Format number of minute to H:mm

I am having trouble with calculating the total time (hour and minute in format H:mm).
Firstly I tried to make its type in Document is Date, but Date type can not sum the total time.
Now I am trying to make its type in Document becomes number, I can calculate the sum but I can not display it in Document with format H:mm (ex: 100 -> 1:40).
I hope that someone can help me with this issue.
Thank you a lot!

Hello, Đinh Quang Linh,

You can use type "Date" with Date contents "Time", it views in forms like HH:mm:ss (you can change view by presentation format). So when you need add minutes you can do it like:
[time = 01:00:00]

time = time + 60 * 60;

a = 100;
H = Int(100/60);
mm = a - H*60;
time = Format(H, "ND=2; NZ=; NLZ=; NG=") + ":" + Format(mm, "ND=2; NZ=; NLZ=; NG=");