You're format is wrong. Try:
=A10-SUM(A6:A9)

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Best Regards,

Luke M
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"Graham" wrote:

Just upgraded to Office 2007, trying to do a very basic spreadsheet and keep
getting the above error message, and I cant see why ?
I have a column, with values in A6:A9, I want to add these together and then
subtract the total from a value in A10.
I'm using =Sum(A10-(A6:A9)), but keep getting the above error ? All cells
are formatted as General Numbers to 2 decimal places.
Can anyone help please ?