You will need to use LEN and build a loop and using INSTR to find the first comma, then add 1 to your counter use INSTR again but move the start point
of the to the next position after the comma, Repeat this process until the end of the memo.
I have attached a zip 2013 version of the database that will count the numbers. The query passes the memo field to the module. The module manipulates memo field to perform the number count.
If you cannot open the database I will post the code on the forum.