Mark
If not familiar with VBA and macros, see David McRitchie's site for more on
"getting started".
http://www.mvps.org/dmcritchie/excel/getstarted.htm
In the meantime..........
First...create a backup copy of your original workbook.
To create a General Module, hit ALT + F11 to open the Visual Basic Editor.
Hit CRTL + R to open Project Explorer.
Find your workbook/project and select it.
Right-click and Insert>Module. Paste the code in there. Save the
workbook and hit ALT + Q to return to your workbook.
Select a range of cells with numbers to sum up on the active sheet.
If you have a Sheet2(or edit Sheet2 in the code to your sheetname) the value
will be pasted there at A1.
Tools>Macro>Macros. Select the macro "Sum_Selected" and run it.
The macro can be assigned to a button or shortcut-key combo.
Gord