I don't know that Excel was the wrong tool for this task. I'm not sure why the spreadsheets couldn't have been distributed and consumed automatically by an Excel application, or at least by helper applications that were fed by and/or into Excel sheets. An Excel spreadsheet is a good enough form; and I don't think replacing one with a webform or pdf form would be any better.
edit: my favorite thing about using excel is that instead of spitting out an answer, you can spit out an Excel sheet that shows a lot of the work itself, therefore partially explaining the answer to the people that have to consume it. The product of your program can often be another program, giving the person receiving the report the opportunity to tweak or add new parameters to your output. Basically currying accounting calculations.
edit: my favorite thing about using excel is that instead of spitting out an answer, you can spit out an Excel sheet that shows a lot of the work itself, therefore partially explaining the answer to the people that have to consume it. The product of your program can often be another program, giving the person receiving the report the opportunity to tweak or add new parameters to your output. Basically currying accounting calculations.