Report Writer GR52 subtotal issue

Hi,

I have a problem when creating a report painter.

I have 3 columns : X001 , X002 , X003

with the formula in X001 = X002 * X003

in the colomn X001 : each row is displayed correctly but not the last row (for subtotal).

The problem is :

the subtotal row is not the sum of each row of the column, 

instead I have this : the ( subtotal X001 ) = (subtotal X002) * (subtotal X003)  <---- the formula is applied to the subtotal

Do you know how to make the subtotal be the sum of each row in my column ? (instead of applying the formula to the subtotal of other colomn ?)

Thanks for your help,

Jo