Is there a way to not have a blank or zero value not be counted in an average
function. Example:

I have a spreadsheet that has a year's worth of data. Currently, it is only
filled in through June. At the very end, I want it to average some of the
data. The formula has 12 cells that I want averaged but if one of those
cells is blank or zero, I want it ignored. 6 of the 12 cells have data.
Right now, I want it to average the 6 cells that have data. Next month, it
will average 7, so on and so forth. Right now, it is taking the 6 values and
dividing by the 12 cells, even though 6 of them contain nothing. I guess I
want the calculation to change as data is entered without having to change
the formula every month and add the new cell. Is this possible??