I encountered this problem and agree it is a short coming. There is also an issue in changing the data type within the excel column e.g form letters to numbers. Working in keyword scripting myself, I tried all the various ways of formatting the data. Non of it worked. I ended up using logic functionality and replacing null fields and other problem cells with the excel data with unique values that when encountered caused test complete to run a "slave" script for the desired action. e.g within a column of numbers null was replaced with an unused number 888 when this value was encountered a script was run that just moved to the next action without entering the value. This was extra work and really time wasted but id did circumvent this problem.
