Line chart problem with Crystal Report

Hi, i am using the Crystal Report that comes with visual studio.net 2003 to do my report. But i have met with some problems when doing the line graph. Here is the problem that i encountered.

I have these data fields from the database.
1) Machine - The name of the machine

2) TimeLog - Every hourly for that machine i will capture some data from the it. (it contains the time when data was captured.

3) outputVol - This contains the data that i have captured, actually it is an output value from that machine.

what i am trying to do is this :
In a line graph : the y axis will be the outputvol
the x axis will be the timeInterval

And for each machine in the database....plot it's outputvol and timeInterval
(I.E if i have 3 machines, i would have 3 lines showing the output vs time in the graph)

I have tried doing it, but it appears that i could only use "on change of" value then show some values. I would appreciate if someone could guide me on the problem that i am facing. Thanks!!