Thank you for your interest in Progress Test Studio.
The described scenario could be accomplished adding a coded step
with few lines of code to transform the extracted value and assign it to the new variable.
Please note that the initial value could be extracted either with extraction step
or in code
and then used in the test. To get the sub-string as per your requirements is a subject of general programming approach which is out of my authority. However I searched the web and found a forum post
that might be helpful for you.
I hope the above details will be useful to find out the best solution for your requirements. Thank you for your cooperation!