How to enter the value of the cell immediately above if that cell = 0

[blueshevy]

Hi
I am in the last stages of setting up a spreadsheet which will help calculate scores in a game we play and need help with the following:

If, within a column of random numbers (calculated elsewhere) there is a 0, what is the value of the number in the cell immediately above the 0, and if more than one 0 in the column, the greatest of these.

I hope that makes sense.

Cheers and thanks in advance
Jan