Automatically add "0" to blank cells without a formula in the cel.
 

I use a spreadsheet that generates projected and actual hours/costs. The
projected hours/costs are generated by general support to a team multiplied
by individual monthly support. The hours are multiplied by a hourly rate. I
have a formula that uses projections if the actual cells are blank and if the
actual cells have value it uses the actual info. I have found it necessary
to add 0 to all blank cells during the months close. I update an average of
5,000 entries monthly and would like to find a way to automatically add zeros
to blank cells on demand monthly without adding a formula to the individual
cell as it creates a VALUE error affecting my roll-up hours/costs. I am
wanting to create an on/off type function if possible.