r - Trying to plot time series data using time information only via lattice

Question

I have a time series data for intraday price changes for different products for example:

Date.Time          Price Product
12/1/2012 13:12:01 15    A
12/1/2012 14:12:05 16    A
15/2/2012 09:09:10 11    B
15/2/2012 08:08:12 10    B

I wanted to plot this timeseries data via lattice to compare price changes between products.

library(lattice)
xyplot(Price~as.POSIXct(strptime(Date.Time, "%d/%m/%Y %H:%M:%S"))|Product, data=temp, type="o")

Because the the day for each product can be several days apart, i would not be able to visualize the price changes over time.

I would like to just plot the time info instead of the full date time info.

How can I achieve this?