Dynamic block that scales based on user input?

Hey guys!

So at my office we frequently have to show circles around objects. The circle's size is based on a multiplier that will vary with project and the diameter of the object. This is super easy math that could be done on the fly when creating a circle. BUT, I'd like to streamline it just a wee bit and make a simple block of the circle that allows for the following user input in the properties panel:

Reference object diameter (Dro): [user types here]

Multiplier (M): [comes with preset value, but user can override here]

And then the linear parameter controlling the circle scaling will auto adjust to reflect:

Diameter of Circle (Dc): D*M

I've dabbled in Vlookup tables/fields/attributes but still on super shaky ground. Any guidance would be appreciated.

Thanks!

Have you looked into 'Cal you can pick say an existing circle get the radius then type a multiplier and it uses this radius for the new circle.

circle pt 'cal (2*rad)

Circle is drawn at pt with 2x ex radius

The reference object will be labeled with a diameter, but it won't actually have a circle of that diameter, so the user will need to input the reference diameter rather than clicking to select it from any existing object.

Got it! Used geometric constraints & the parameters manager.

Symbol - Tree CRZ.dwg