Dividing by column in another table

Hi

I have a bunch of em_codes associated with my calculated column ALRemain. I want a new column which divides the ALRemain by a value associated with the em_code (the hours column), which can be found in my EmCode Table.

What would be the best method to achieve this?

Thanks

Image may be NSFW.
Clik here to view.AL RemainImage may be NSFW.
Clik here to view.EmCodes Table