When a value is entered into Cell $B$41 it must not cause the Sum($B$24:$B$40)>300. If it does, it will output "x". If it does not then print the value in cell $b$41. I am trying to embed this into an existing If/and statement. This existing if/and function exist in cell $D$20. Does anyone have any pointers?

Thanks for any help in advance.