Excel 2007 : How to copy from one sheet to another without freezing

Hi All

I have written a stock control programme using excel

I have sheets from 1 to 30

When I try to copy of say sheet 17 to sheet 18

Excel hangs and i get an error stating that resources need to be free


Any help here would be highly appreciated


Kind regards

Raj

Each month I have to clear the data for the next mont is there a way around to clear the sheets automatically without changing the formula

Am attaching my spreadsheet

having a prob with uploaded 2.5mb file