Simulate Electric field

[shaji]

Hi All,
I am trying to simulate electric field lines between two different charges, charges can be similar or dissimilar.

I have a sample representing what I need

http://www.colorado.edu/physics/phet/simulations/chargesandfields/ChargesAndFields.swf

I only need to rotate the arrows as and when the charges are changed or distance between the charges are changed.

Any help in this direction would be appreciated.