Unity UI help to fill player position on UI

hello!

i have my player moving on the worl x axis, and some kind of map to show where actually he is, on this map i have some red zone, want i want to be able to do is to say, when you are in the red zone this event occur, i was able to set the first one red zone, and i'm able to move it but want i nedd is something like this :

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left center right

if this zone is small than the last one, i need to change it's scale on the X axis, but how to do it dynamically connected to the meter value of my world scene?

sorry for my English.. i hope that's clear... if not please let me know it...

thank's in advance for anyone that will try to help me