Sorry

[Robert Brenstein]

>More likely the field "price" contains something Rev refuses to 
>parse as a number (make sure the field contains exactly a number, 
>and nothing other than the number, which might confuse the parser).

My guess is that your price uses comma as decimal separator whereas 
Rev expects it to be a period. If your field should display commas 
per country convention change

put length(field "myFld") * field "price" into fld "devis"

to

get fld "price"
replace "," with "." in it
put length(field "myFld") * it into fld "devis"

Robert Brenstein