irregular ordered list syntax

G'day,

Can anyone suggest the best way to structure the following sort of data:

	Heading
		Subheading
			1: stuff 
			2: more stuff
-->			5: jumped over some numbers there
-->			9: and we're through

Basically I'm pulling some fairly heavily nested hashes out of a
YAML file.

I've searched for options to customise the format of an ordered list,
but came up with nothing.

Any ideas most appreciated!

Thanks,