FormCalc Time Calculations

I'm using the below formcalc script to calculate the difference from a start time to a finish time. What I want to see is something like:

Start    Finish  Total

1800    1932    1:32

Using below I get the right amount of minutes but it always shows as a decimal for example 5mins would be .0833333 or 1 hour 5 mins = 1.0833333

I have tried everything please help!

$ = Abs(Time2Num(Row1.StartTime.formattedValue, "HH:MM") - Time2Num(Row3[0].EndTime.formattedValue, "HH:MM")) / (60*60*1000)

Also if possible I need this to work past midnight for example:

Start    Finish  Total

2300    0118    2:18