entering null values

Doug, Thanks for the detailed response. A couple of quick questions. After taking a quick look at the script with an inexperienced eye, it looks to me that the null value is entered when the user enters a '0' in the form. If this is the case it may present another problem. This application is being used to track student points in a program in which they can earn 0-100 points each day. I am attempting to use the null value to account for absences when totaling weekly percentages. Therefore I must be able to differentiate between a day when a student is absent and a day when a student earns 0 points. Each would have a very different effect on the student's weekly average. If I am wrong about this, then what value would a user enter in the form to submit a null value.? Also, it looks to me like this script will work for null and non-null values, but I just wanted to be sure. Again thanks, Scott Wagner