xforms-value-changed

Hello everybody!

Recently, I came upon a thing I could't implement in my form without a 
hack-like trick.

I have a <setvalue event="xforms-value-changed"> element nested in 
<select1> (well, actually, the type of control doesn't matter). When 
setting the value, I need to know both values: the one that element had 
*before* the change happened - and the one it has *after* change.

I believe this feature could be useful to many. Possibly, the spec lacks 
something?

I can provide an example of what I am doing - to be more clear.

Regards, Victor.