i used some time a spreadsheet like this:
cam | sT | eT | s$ | e$ | tT | t$ | $H
cam1 | 14:00 | 18:00 | 320$ | 420$ | 4h | 100$ | 25$/h
cam2 ...
you just had to put start& end times as well start&end money .. rest are simple formulas ..
Software OpenOffice (calc) is free and as good as MS Excel
you can build up the whole month and then just copy (incl. all formulas) and paste. you get also total earned /month etc. anything you want.
imho - best way to do it.
