Assign distance variable value from 'Find Me' to a 'BLL' variable

I’m trying to track the distance someone is from home using the ‘Find Me’ app.

When they leave I set a BLL variable ‘distance’ to 0.

A When triggers when the ‘Find Me’ variable ‘#Distance from Home(y) in mi becomes greater than ‘distance’. The Then tries to set the BLL ‘distance’ variable to the value of ‘#Distance from Home(y) in mi’ so I can determine if they are coming nearer or moving away.

Unfortunately the ‘distance’ variable doesn’t change.

I am using the tag system to select variables.

Is this possible? Is there a syntax I need to use (e.g. {[]}). Does ‘Find Me’ need to support BLL?

All help is appreciated.