Format a function field

Format a function field

How do you format the number output of a calculated field?   I cannot use the currency fields as I deal with too  many different currency types.  I'm calculating the following fields:

Revenue Per Media Area * Number of aircraft. 

The results shows xxxx.x (1 decimal)
I need the result to show xxxx.xx (2 decimals)

One of my fields is set to 0 decimals (and it cannot change)
One of my fields is set to 2 decimals

Thanks!

PS.  I'm a beginner beginner so please respond in simple terms.  :)