Dynamic thresholds runtime C#

How do I adjust threshold in a runtime for SPECIFIC blend tree via code? I saw some things like in blend tree class and animation state. But how do I connect these to specific blend tree? Please include small snippet if possible. 172323-capture.jpg

I found out that I can keep thresholds between 0 and 1, then scale it by dividing the current velocity by max velocity.
Slipped through my mind.