If I remember right if you just leave the cell in the spreadsheet blank I don't think the variable in your script will be set to NULL. I think it will just be unset and an error will return if the script trys to use the variable. If this is what you are seeing then you may need to add code to set the variable to NULL if there is nothing in the spreadsheet.
I am not 100% sure on this. Just trying to remember from a past experience.
Yes, by a table I meant a spreadsheet. I am using SilkTest's DB_Tester functions with an Excel spreadsheet which so far works quite well.
My problem was that I had one (string) column with cells that sometimes contained no values and when I tried to run my testcase it would give me an error because the that particular cell didn't contain a value. I thought maybe there was some way you could set a column to be allowed to contain null values. . .
However, I've managed to work around this problem by adding the following code to my test case:
if (Data.sParent != NULL)