When occured the error - already by the first iteration or later? If later it would mean that your script is generally working but a certain combination of KVKNO and table @1 isn't available. If it's by the first iteration you should check if the variable KVKNO contained a valid content, for example with:
trace '$(KVKNO)';
If this looked ok. you should check if your load-statement is right - just create a load-statement with the wizard of one and/or several pages and compare this result with your code - maybe there are differences.