NagiosGrapher question

I want to generate a rrd graph from the output of the “check_multi” plugin, but the tricky part is that the output is show on several lines.
Something like this:

OK - 2 plugins checked
1] Server1_disk C:\ - total: 19.99 Gb - used: 0.13 Gb (1%) - free 19.87 Gb (99%)
2] Server1_ping OK - rta 0.368ms, lost 0%

Is there a way I can generate a rrd graph for the disk or the ping check?
In the nagiosgrapher log, the perfdata value is recognized as “OK - 2 plugins checked” and the other parts of the plugin’s output are left out.