If A1 is blank, B1+1.

B1 may be an error. If B1+1 is error, C1+1

C1 may be an error. If C1+1 is error, D1+1

This is what I have come up with, but it doesn't work: =IF(ISBLANK(A1),B1+1,IFERROR(B1+1,C1+1),IFERROR(C1+1,D1+1))

Thank you in advance!