Reference dimension in a sketch?

Hi,
A bit tricky to explain but I'll try......!
I have inserted a new sketch in an assembly to show the path of rotation of a part if it is rotated between two locations. The sketch
is a construction line circle, the diameter of which is mated to the same point in each of the two modeled parts. The two modeled parts are located in the two possible locations for the part. The centre of rotation can be moved by dragging the size of the circle. The larger the circle, the smaller the angle of rotation between the two positions. At the same time the location of the centre changes, getting either nearer or further away from the points on the parts.
Having drawn lines between the circle centre and the reference point on each component, it is easy to measure the angle of rotation using the measure tool.
While experimenting with an assembly and trying to achieve an optimum location for the parts, I have to keep measuring the angle because I need to consider it's effect on another feature. Is it possible to insert a 'driven' dimension that changes dynamically with the dragging of the circle but does not define the sketch? A bit like a reference dimension in a drawing.
All a bit much for a Saturday I know but if anyone can help it would be appreciated.
Flynt.
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I didn't know that! Yup!, just found out how! It's an option in the 'more properties' box selectable at the bottom of the Dimensions tab. You learn something every day!!
F
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