calculating grand total on report

[emmily11]

i have a report called invoice and fields calld quantity and unit price i have then calculated these in the form to give a total for each product in the page footer i am trying to calculate all the numbers in the totals colum and have tried everything i can think of please help
at the minute i have

=Sum([Quantity].[Text])*Sum([Price Per Unit].[Text])

in the grand total but this gives a #Error

thanks
emmily

 

[Rich]

Article ID: Q132017