Hi,

Assuming the number is given in an Excel Field named 'Test', a PSM expression displaying the double of this amount could look like:

Code:
STR(VAL([Test])*2)
i.e. convert [test] into a number (with VAL), then multiply it by 2 (with *), then reconvert the result back into a string (with STR) so that it can be displayed on the page.

Hope this helps!

Benoit