live cycle calculations

Hello,

I have made form using adobe live cycle es2 : I have numeric fields that I want to get their median ... I know that there is average in formcalc but for example:

Cell 1=  5

Cell 2=  3

Cell 3=  6

Cell 4=  2

median is = (5+3+6+2)/4    the 4 is the number of cells.... this is easy to obtain

my problem is that if one cell is empty or = 0    so I need to exclude this cell from the equation for example:

Cell 1=  5

Cell 2=  3

Cell 3=  0

Cell 4=  2

here I don't want to include cell 3 because it is = 0 only I want (5+3+2)/3

please can any one help me....

thanks