Formula for counting back cells with zero (until positive value)

Hi all, new to the forum, and i've been thankful for everyones expertise over the years.
I have a formula question that i cant seem to crack.
I have a massive accounting spreadsheet that managing incoming monthly payments from customers, and unfortunately, some dont pay each month, and i need to know how many weeks pave passed since last payment.
I need a formula that looks back (right to left) and shows how many zeros ($0.00) there are until it hits a positive amount.
The attached sample shows this better. Column Q needs the formula, and the numbers in red are the right answers. The greyed cells are what the formula needs to count.

Any assistance here would be truly appreciated.

thanksExcel Sample Sheet.xlsx

Put this array* formula in Q2:

=15-MAX(IF(B2:P2>0,COLUMN(B2:P2)-1))

then copy down.

*Note that an array formula needs to be committed using the key combination of Ctrl-Shift-Enter (CSE) instead of the usual <Enter>.

Hope this helps.

Pete

Genius, thanks mate.
And quite a simple solution now that i see it!

cheers