Thank you for a quick and helpful suggestions.
Your method, putting x^2 + ^y2 -1
in dynamic works in our routine to solve our real problem.
However, in our problem, this method, keeping
the dynamic property of x and y is not necessary
and it seems introducing complication.
It is indeed nice that the values always respond the mouse position,
but for us it is not nessary.
We wish strongly to work 'outside the module' rather than
staying inside the module after selecting the coordinates of points
by the mouse click measurement.
In the subsequent procedure, the dynamic property
is no longer necessary. We only wish to use the obtained values
just as usual static variables.
How could we 'UNWRAP' the dynamic property ?