Setting fixed prices on non fixed cost?

I'm wondering whether any of you use services from outside your country to provide a service inside your country. If so, how do you go about setting your prices? For example, if I had a website hosting service but i was actually a reseller for another company outside my country, how can I work a price around to ever changing currency?

I mean I cant keep changing the price everytime the dollar goes up and down.

There are several routes you can take:

1. Set the prices in the currency of the source of your service. This way you don't have to worry about currency fluctuations as you will always charge enough to cover your costs. Of course there are countries that don't allow it so you may have to choose a second route.
2. Set your own currency exchange rate. This will basically fluctuate your margins as currency fluctuates but normally during the week currency adjustments are not significant enough to worry about it (well in most cases they aren't). Barring some significant turmoil within the countries whose currencies you are exchanging.