Average Formula With Empty Cells

I have a grade system where I need to obtain an "Average" of grade data within four cells. At time there may onlt be two cells with a value or three. Example: The cell cell cantain a value of 100 points with the totral of 400 point. AS we know the "Average" would be 100 points. But is only two cells cantained 100 point and the other two where empty then the "Average" come back as 50 points. Because I have 4 cells that requires a value input. So my question is how do I create a formula that will give the correct value for the "Average" of data that is placed in the cells. The values are calculated as a total from the grades entered. That total is in F14, F31, F48, F65 - Now if F14 has a value of 100, and F31 has a value of 100 then the "Average" should be 100, but it is not for the is calculating F48, and F65 as 4 values, so the return is 50. The situtation is that I need all the cells for in some cases data will be necessary, but I need the "average" to be calcalated for only the values entered.

Where is the Formula.
=IF(SUM(F14,F31,F48,F65)=0,0,AVERAGE(F14,F31,F48,F65)) - My brain says this is simple but no matter what I do it returns 50.