Reset Frame size

NB: This is purely using "Javascript"
How do i change the frame sizes at the Client side???
For ex: I have an Html page divided into 3 Horizontal rows using the <Framset> Tag (assume 30%,40%,30%). In the first row i have an hyper-refernce <a href> Tag. On clicking the hyper-reference i want the first frame to decrease in height ie it should decrease to become (20%) and the second frame height should increase to become (50%) such that the page is resized at (20%,50%,30%) from the initial (30%,40%,30%)
This has to be done at the Client side itself

Would appreciate if anybody can help

Its very urgent !!!!!

Thanks

Regards
ashvin