Building complex formula without VBA

I need to use the information from one workbook to populate another.

I want to search an entire row and identify the last time a specific value (number or text) appears in that row.
Example: Range is A1:A15 and and the number 9 appears 8 times, i want to know the cell that it appears in last. If that is cell A12 I want to return the value of I12 to another workbook.

I can't use VBA.