Speeding Up Excel
Once you have used Excel for awhile you will discover that your spreadsheets increase in size and complexity and start to slow down. At this stage you may want to consider ways of speeding up Excel.
Unfortunately there are no quick fixes and normally it is just a case of improving the design of your spreadsheet or financial model to perform the calculations in the most efficient and effective manner.
There is a very useful article on the Microsoft site (http://msdn.microsoft.com/en-us/library/ff726673(v=office.14).aspx ) which explains some of the better ways.