A couple of comments. First, the post from the Anonymous Monk is correct about the column numbering. In the OLE environment, Excel's columns and rows are 1 based and 0 based. In other words, the upper left most corner cell is row 1, column 1 or A1, depending on which cell reference scheme that you're using.
Secondly, I personally would discourage the practice of writing your code such that it takes over an active instance of Excel. For more info, check out the posts from me and davies in "use Win32::OLE::Const" not having an effect and Perl r/w Excel with OLE. (If you believe that davies and I contradict each other in those threads, I'd recommend going with what davies says since he's far more knowledgeable with both Excel and OLE.)