multiple IF functions

My boss has tasked me with reviving the formulas we use on our time sheets. What I am having a problem with is a particular formula.

B1 and B2 are merged and centered
A1 and A2 can have "OFF" in both cells, or have a time.
The time in A1 will be the "in" time
The time in A2 will the the "out" time.
If there is OFF then then "0" will be in the merged B cells, if a time then it will be A2-A1=#of hours in the merged B cells
I cannot get the formula to work.

Thanks for all the help

Try putting this in B1:

=IFERROR(24*(A2-A1),0)