How can I plot bounce rate over time?

Hi :)

I have a search that calculates the Bounce Rate for a web site:

source="web" configuration.client.company=foo event.type=page_view 
| stats dc(event.id) as eid_dc, c(event.id) as eid_c by session.id
| addcoltotals 
| eval BounceRate=eid_dc/eid_c
| stats last(BounceRate) as BounceRate

At a high level, it calculates the BounceRate by dividing the total number of distinct urls (ie. eid_dc) by the total number of urls (ie. eid_c) by Visit (ie. session.id)

I would like the ability to plot the BounceRate over time, but I can't get timechart to do the needful... any help will be greatly appreciated :)

Luke.