Plotting seperate time functions on the same graph

Allow me to clear the question up, I have the following data (this is a sample).
I want to plot the second column as an area chart, and the third column as a line chart, on the same graph. I want to plot them both against the time axis (first column). The blanks are not zeros but an absence of data - hence the line chart should have fewer points. I just can't crack this one, so your help is much appreciated.

Martin

28/05/2009 08:05 2447.38 3.100582032
28/05/2009 08:06 2449.88
28/05/2009 08:07 2448.47
28/05/2009 08:08 2451.4
28/05/2009 08:09 2453.27
28/05/2009 08:10 2454.27 4.177587402
28/05/2009 08:11 2455.61
28/05/2009 08:12 2454.33
28/05/2009 08:13 2454.33
28/05/2009 08:14 2455.51
28/05/2009 08:15 2452.43 1.368588315
28/05/2009 08:16 2451.1
28/05/2009 08:17 2450.31
28/05/2009 08:18 2449.35
28/05/2009 08:19 2451.84
28/05/2009 08:20 2452.94 0.516733621
28/05/2009 08:21 2451.63
28/05/2009 08:22 2452.91
28/05/2009 08:23 2453.21
28/05/2009 08:24 2455.43
28/05/2009 08:25 2457.13 0.252197604
28/05/2009 08:26 2456.17
28/05/2009 08:27 2458.26
28/05/2009 08:28 2458.55
28/05/2009 08:29 2457.17
28/05/2009 08:30 2457.28 0.462292438
28/05/2009 08:31 2457.28
28/05/2009 08:32 2456.89
28/05/2009 08:33 2457.13
28/05/2009 08:34 2458.94
28/05/2009 08:35 2455.12 0.246397505