calculating wages

I am trying to create a spread sheet that will automatically tell me what my check should be before all the taxes and stuff are taken out.
I have a cell that shows how many hours I worked in the week. I know how to calculate my hours times my wage. I need to figure in OT. I know what the sum of 40 hours would be, but if it is 41 then that 1 hr needs to be calculated at time and a half. Any ideas on this?
If not I will just do it the old fashioned way.

John