HI

how to write a mel script  that controlls same attribute from the selected list;

example:
I created 5 curves and made them dynamic curves by going to hair menu and clicking  on make selected curves dynamic.now
for all these  curves i want to  controll  the stiffness scale attribute  at a time by gradientControl(i.e  if i add a new gradint point on curve 2 it has to update on all other curves)

gradient controll is ui widget not a node data needs to come out of a node (which in turn may be manipulated with gardient control). You could use a remap value node.

Mel is not supposed to dio the work, melis supposed to decribe the work.