Is it possible to get the target css property value during a css3 transition in Javascript?

Is it possible to get the target css property value during a css3
transition in Javascript?

I've two divs positioned absolutly and I position them relative to each
other. When width of one is change, then i recalculate and set positions.
While I use css3 transition on 'width' property, when i try to get 'width'
of animated one, it gives me the current value on dom. But i want to get
the target value of transition to set positions correctly on begin of
transition effect. Is this possible to get the target value via javascript
or other ways?
EDIT
Below is a jsfiddle demonstrates my issue. It alerts '100px' but I need to
get '300px'.
http://jsfiddle.net/Mdbgs/
Thanks.