In a word, no.
Once you have reached 5 authorized computers and some of the authorized computers are no longer available to de-authorize from the computer, you can de-authorize all followed by re-authorizing the computer or computers current being used.
http://support.apple.com/kb/HT1420
+To deauthorize all computers associated with your account.+
+If you find you have reached 5 authorizations, you can reset your authorization count by clicking Deauthorize All in the Account Information screen.+
+Click iTunes Store in the menu on the left side of iTunes.+
+If you're not signed in to the store, click the Account button, then enter your account name and password.+
+Click the Account button again (your ID appears on the button), enter your password, and then click View Account.+
+In the Account Information window, click Deauthorize All.+
+Note: You may only use this feature once per year. The Deauthorize All button will not appear if you have fewer than 5 authorized computers, or if you have used this option within the last 12 months. If you need assistance on using this feature, please contact the iTunes Store support via email (
http://www.apple.com/support/itunes/ww/).+
