Busy week, this time I'm not as fast!

So, your real issue (or first issue) is the empty cell messing up
other formulas. I'm not sure which formula is in the Price cell in
Sheet1!D1, but this should get rid of that error. You would just put
in your entire formula, minus the = sign:
=IF(B1="","",yourformula)

If the error still pops up, it is because of your formula, not because
of the empty B1. And that would need different testing.