Find text bounds from part of MText

I have a quick question: Is there a way (any way) to obtain the bounds of part of a MText string. I manage to get the line of the string but I would like to go further and get the exact bounds of the substring.
Main goal is to create hyperlinks in de PDF plots, I am trying to avoid too much hyperlink area in de PDF plot.

At the moment I get the MText from leader and explode to Text. For every Text I evaluate the bounds and verify with regular expression the reference.

I would like to find the geometry of the substring but have no idea how to with the textstyles and character spacing being different. Example below.