OK, so that worked, but there are some times where I dont have a completion date, so that cell is empty. Using the network days function that is giving me these huge negative numbers, which is now throwing off my lead time average.
This is the formula I was using, but now it is not accurate.
=AVERAGE(IF(ISNUMBER(P3:P10),P3:10))
I tried doing this
=AVERAGE(IF(ISNUMBER,">=0"(P3:P10),P3:P10))
but that is giving me an error.

Would this be the best formula to use then?
=AVERAGEIF(P3:P10,">=0")

Thanks for all the help so far.