Subtracting numbers in cell from another cell while ignoring the letters

Here's what I've been trying to figure out for the last several days...

My boss wants to keep an accurate count of parking lot spaces from several of our lots on a daily basis. Often these lots get leased and currently my formula adds the number of spaces in each lot from the total if the cell is empty. Additionally they may lease a lot to provide extra parking which is then added if the cell has anything in it. Finally there are always a certain number of parking spaces which vary day by day and are deducted from the total. What I am trying to figure out is how to put random numbers in the cell along with the text which shows who is leasing the lot and deduct just the number from the total.

This is the current formula I've created.
=SUM(SUMIF(C5:T5,"=",$C$35:$T$35))+(SUMIF(W5:X5,"*",$W$35:$X$35))-(SUM(Z5:AB5))

Example:

C5 has XYZ in the cell, nothing is added to the total, if it is blank the value in C35 is added. If XYZ 234 is in C5 I would like to subtract 234 from the value in C35 and add the remaining to the total.