Here is example http://jsfiddle.net/rigaconnect/gLCjy/14/

Enter something in left top field. Right top field value changes to 1. That is ok.

Then press and hold ctrl and click in left bottom field. Left bottom field value becomes the same as left top field's value. This is also ok.

But right bottom field value does not change. This is the problem... Actually no idea. Need advice to which direction to go....