TRUNC formula

I've run into a problem with a formula I need to subtract time code from video tape. An example of the time code looks like this: 2.21.03

2 = hours (made up of 60 seconds per hour)
21 = seconds (made up of 24 frames per second - film speed)
03 = frames

I've been able to truncate and then subtract the following: 21.03 less 22.19 = 1.16 (or 1 sec 16 frame difference).

I've attached an Excel sheet example to show you.

What I'm after is expanding this formula to include hours in the equation.

Help!