I developed a tool that creates any of three worksheets, based on the data in a file,and then a chartsheet for each. Everything was going smoothly until today when I tried to run todays new data and excel dropped core. I narrowed it down to two of the three chartsheets, if generated, cause it to do this. I can still run the old data files and they work just fine. This data file has no surprises in it. The charts all use the same formats. Any ideas on how to figure out what is going on here.