directly automatic colorchange

[yxj0312]

Hi,
is it possible to add a feature with a plugin like:

first all the nodes in the graph were colored according to the distance.
when i drag 1 node in my graph, it can automatic show the Coloringchange in the Overview or Preview window.

i have already write 1 Plugin to implement this features. But i need to manully click the bottom which i designed in the statisitikmenu to calculate the distance each time.

My question is: is there some API to support to directly automatic colorchange after change the position of nodes

thanks