Field height Adjuster Button

[Sannyasin Sivakatirswami]

Has anyone already scripted a button has the appearance of a "split 
window pane" heights adjuster that operates on two horizontally 
adjacent fields?

I can start on this myself, but thought it might already be done.

Visualize two fields, one above the other with the bottom of one field 
contiguous with the top of the one below it.  In between , if you click 
down a button appears that indicates it can be dragged up or down and 
the relative height of the fields will change as well as (obviously) 
the top coordinate of the bottom field as the one above it grows or 
shrinks, the top field topLeft coordinates would be fixed, as well as 
the bottom field's left coordinate.

The same algorithm could then be applied to the widths of two fields 
adjusted along their vertical contiguous border.

What I need doesn't have to be a polished gem in terms of HIG, just 
functional.

Sivakatirswami