Indirect and Address w/in formula

Hello,

Can you tell me exatcly what the following formula is supposed to do:

=IF(ISERROR(F29),0,LOOKUP(C29,INDIRECT(ADDRESS(F29,5,,,F$1)):INDIRECT(ADDRESS(F29,15,,,F$1)),INDIRECT(ADDRESS(F29+1,5,,,F$1)):INDIRECT(ADDRESS(F29+1,15,,,F$1))))

I have a previous employee's spreadsheet that needs changes made to it. All but a couple items come out w/correct new data when the changes were made. Those that don't come out w/the correct new data, appear to have the same formula as those that do. So, what I'm trying to figure out is what the above formula is exactly telling the cell to do.

Thank you.