Group and compare data

I have som XML that looks like this:

<Forhandler>
	<Forhandler>
		<navn>Dealer name</navn>
		<email>mail@xxxxxxxxx</email>
		<adresse>road 11</adresse>
		<postnr>9999</postnr>
		<by>city</by>
		<telefon>4444444</telefon>
		<aabningstiderMan>7:30 - 17:30</aabningstiderMan>
		<aabningstiderTirs>7:30 - 17: 30</aabningstiderTirs>
		<aabningstiderOns>7:30 - 17:30</aabningstiderOns>
		<aabningstiderTors>7:30 - 17:30</aabningstiderTors>
		<aabningstiderFre>7:30 - 17:30</aabningstiderFre>
		<aabningstiderLoer>10:00 - 14:00</aabningstiderLoer>
		<aabningstiderSoen>Efter aftale</aabningstiderSoen>
	</Forhandler>
	<Forhandler>
		<navn>Another dealer</navn>
		<email>another@xxxxxxxxx</email>
		<adresse>another road</adresse>
		<postnr>5555</postnr>
		<by>big city</by>
		<telefon>5555555</telefon>
		<aabningstiderMan>07.30 - 17.30</aabningstiderMan>
		<aabningstiderTirs>07.30 - 17.30</aabningstiderTirs>
		<aabningstiderOns>07.30 - 17.30</aabningstiderOns>
		<aabningstiderTors>07.30 - 17.30</aabningstiderTors>
		<aabningstiderFre>07.30 - 16.00</aabningstiderFre>
		<aabningstiderLoer>Lukket</aabningstiderLoer>
		<aabningstiderSoen>Lukket</aabningstiderSoen>
	</Forhandler>
</Forhandler>

What I am trying to accomplish is to group the opening hours so they
look more nice.

For the first dealer the result would be:
Mon-Fre 7:30-17:30
Loer 10:00 - 14:00
Soen Efter aftale

For the second dealer the result would be:
Man-Tor 07.30 - 17.30
Fre 07.30 - 16.00
Loer-Soen Lukket

I have tried som xsl-choose loop, but I went sour in the complexity of
variations, what if a dealer have diffent opening hours every day of
the week.

So I thought, there must be at better approach on how to achieve this.
Is the use of keys a better approach, and if so, how?

/Thomas