Ongoing Average Calculation
 

I have a spreadsheet created that receives data input throughout the month.
Once the whole month is filled in and the extra blank rows deleted there is a
calcuation at the end that tells the average of row Q. It always shows ####
until all the rows are either filled in or deleted. is there a way to have
it calculate the average on an ongoing basis and when new data is input it
will consider that in the calcualtion as well?

Thanks,

Tania