Hi Joe,
Perhaps

Calculation takes forever, MS KB Q243495 XL2000:
Calculate Message Remains in Status Bar If 65,536 Formula
References (Xl97 and XL2000),
http://support.microsoft.com/default.aspx?kbid=243495

Since you mention changing SUM, hope you are not trying to use
SUM as a running balance.

Use of SUM Worksheet Function for running balances as in =SUM(D$2:D2)
filled-down can take excessive time. Use of
SUM is fine for simple totals but not for running balances. see
Slow Response, Memory Problems, and Speeding up Excel
http://www.mvps.org/dmcritchie/excel/slowresp.htm

Sometimes the use of the ultimate Calculation shortkeys
will break things loose that F9 (calculate) would not
-- Recalculate all cells on all worksheets in all open workbooks [Ctrl+Alt+F9]
---
HTH,
David McRitchie, Microsoft MVP - Excel [site changed Nov. 2001]
My Excel Pages: http://www.mvps.org/dmcritchie/excel/excel.htm
Search Page: http://www.mvps.org/dmcritchie/excel/search.htm

"Joe" wrote in message ...
Hello

I have written a fairly big spreadsheet linking through the pages with SUM,
SUMIF and SUMPRODUCT formula's

What I am now finding is that when I update one page it doesn't update the
rest, even if I am only typing in a figure to the SUM function.

I have check and the calculations function is on automatic.

is there a fix or something that I could run to make sure that all the
formulas are working correctly.

thanks