Starting in Cell AI8, calculate the next sequential number using the last number from Column B. But only calculate for Cell AI8 if AG8 = "1'.

In the screenshot attached, Cells AI8 and AI9 should remain blank. AI10 should be 1261. AI11 should be 1262. AI12 should remain blank because AG12 is blank. The next sequential number should be 1263 in AI18.