Batch compare (difference calculation) in PSP X2

Hi
I am new here and to Corel as well.

My intention is to use it for following task:

I have lot of images in specified directory (mostly *.jpg or *.tif) and I have corresponding *_filtered.tif files in the same directory (no jpg anymore). The filtered files can be moved to another directory if it makes the task easier...

I want to compare all pairs of images which involves:
load image1.jpg
load image1_filtered.tif
use arithmetics (x-y+128)
(maybe add contrast here)
save image1_diff.tif (or jpg)
go for next image

The purpose is to see how much improvement/damage is made by the filter used on the images previously.

Thanx
R*