Excel has great support for AppleScript which in principle makes what you're trying to do somewhat more straightforward.
I can get you started with a KM subroutine I wrote to help another user out: it lets you read data from cell(s) in an Excel worksheet. You can find it here;
The original thread that led to this subroutine is here:
In terms of incrementing row and column indexes and testing a cell for emptiness is not really too difficult to do in KM.