XIRR Formula - Summing Total in alternate column

Question

Struggling to think my way through this. Have borrowed the formula from another on the forum.

The Formula works fine if the current value of the stock, marked orange, is in the same Column as the purchases, but I have my current values in an alternate column (As shown in snap) I am sure there is a simple solution, can anyone offer some suggestions?

And the formula is

=XIRR(OFFSET(AC$9,MATCH(AA9,AA$9:AA$17,0)-1,0,COUNTIF(AA$9:AA$17,AA9)),OFFSET(AB‌​$9,MATCH(AA9,AA$9:AA$17,0)-1,0,COUNTIF(AA$9:AA$17,AA9)))

Show Image

Thanks!