Thanks for the reply Oxa. The problem I am having is that error messages appear when I try to run my program on my new computer. The program takes data from the worksheets created by MF and uses the data to perform calculations in another workbook. This worked fine on my old computer (using marketfeeder 5), but I get both "Abnormal Termination" and "Thread Creation Errors" on my new computer. I am using Marketfeerder 6, but with all the same settings as before. My new computer is a quad core with loads more ram than the old one, and it does not look like the memory is been used to the limit. Also, I am using Windows 7 on the new machine (vista on the old one). Can you suggest what might be causing the problem? I thought it might be a problem with timing, since my program executes much faster on the new machine, but perhaps it is something else that I am missing. Would it be possible to download a copy of MF version 5 to see if that is making the difference?