=if(Input_Sheet!M3="","",Input_Sheet!M3&-8007004)

Will make this cell blank if M3 is a blank cell (Truly blank, that is, no
space in there). If the cell is not blank, it will append -8007004 to it.
Presuming you want it to read like this, not do the subtraction itself.

"Jim" wrote:

Hello,

I would like to add to functions to this formula:

=Input_Sheet!M3 (it currently put's out this result: 44247896)

I would like to add: 800704 to the result so it reads: 44247896-800704

and I would like to learn how to write this formula so that if it refers to
a blank cell it does not return an error (it remains blank as well.

Thanks for the help.
Jim