Custom Number Format for Feet and Inches?
 

After creating the custom number format and setting that format to a cell, I
would like to enter a number like 12.5 and have 12'-6" returned.
The following custom format works (#'-#\'), but I need to know what to do
about the math. For instance, 0.375 will either equal 3/8" or 4 1/2"
depending on whether 0.375 is feet or inches. (0.375 inches = 3/8" and 0.375
feet = 4 1/2")