How can I check with a regex that a string contains only certain allowed characters?

I need a special regular expression and have no experience in them whatsoever, so I am turning to you guys on this one.

I need to validate a classifieds title field so it doesn't have any special characters in it, almost.

Only letters and numbers should be allowed, and also the three Swedish letters å, ä, ö (upper- or lowercase).

Besides the above, these should also be allowed:

• The "&" sign.
• Parentheses "()"
• Mathematical signs "-", "+", "%", "/", "*"
• Dollar and Euro signs
• One accent signed letter: "é". // Only this one is required
• Double quote and single quote signs.
• The comma "," and point "." signs