Excel file runs slowly

Hi Again

I'm working on a spreadsheet which includes some array formulas, with no macros, in about 5x200 cells. The file is only about 120lk. However, when I try to filter the data, or save the worksheet, it runs incredibly slowly for about 5 minutes, and I can't do other tasks. I managed to get task manager open and the CPU was at 100% usage. Surely Excel should be able to handle this?

I've attached the file. It's still a work in progress, but just wondering if anyone had any ideas for fixing this problem?

Thanks