1. You should have copy/pasted the actual formula from the cell.
2. You are using the word 'blank'; however, you are testing for a space, (" ") in the formula. A (" ") is an actual character just like the rest of those you see here.
3. Your formula is saying: IF there is a space character in D10, insert the character string "(636-((D11*12)+E11))/636", * Notice that the quotes make this a character string, not a formula to be calculated/evaluated. *, ELSE write a space character (" ") to the cell with the formula.
4. One way to check if two cells are empty, i.e. (""):
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