Suppose, your names seperated by "," is in cell A4.
Here is the formula to calculate number of commas in the cell A4:
=LEN(A4)-LEN(SUBSTITUTE(A4,",",""))
The first part: LEN(A4) calculates length of string with commas.
The Second part: LEN(SUBSTITUTE(A4,",","")) calculates length of string without commas.
The differnece of the two i.e. first part-second part will give you number of commas in your string.
This formula can come out handy in many calculations.
