How to check if the != null fields in coumn 2 have a certain value

I have a form with a table that is 15x9.

In column 2 if any of the != null fields == 300 && any one of the != null fields does not == 300, I need an error message saying all to be = 300.

If all of the != null fields are == 300 then no message

If none of the != null fields = 300 the no message

It does not need to change the values, just display a message.

thank you in advance