SetTextScaling + Align Right problem

I found a problem with the text scaling
I'm drawing Right-Aligned fields on a pre-printed module
PDF lib version = 4.41 (I think I don't need to update it because I didn't find any fix I really need, and because I will need to update it in every place I use the software)
Measurement Units = mm
Origin = top left
Language = VB

Since the scaling with Left-Align works right
Draw Align Left, scaling 100%

------------------ |XXXXXXXX        | ------------------

Draw Align Left, scaling 50%

------------------ |XXXX            | ------------------

the problems come with the Right alignment

Draw Align Right, scaling 100%

------------------ |        XXXXXXXX| ------------------

Draw Align Right, scaling 50%
I got

------------------ |        XXXX    | ------------------

but I expected

------------------ |            XXXX| ------------------

I'm trying to fix it by moving the text right of the difference between the text width = 100 and the text width = myTextScaling

offset = GetTextWidth(text) - ((GetTextWidth(text) / 100) * myTextScaling) DrawText x + offset, y, text

I need obtain the scaled text width by hand because GetTextWidth() returns always the width at 100%
The problem is that the offset I calculate is never accurate and the text is printed always at the wrong position

Thank you for any help,
Daniele