RSA with public key for Decrypting?

I need to create some security for an application I'm working on and
I'd like to do some sort of asynchronous encryption like RSA.  What I
need is an ecryption that has a public key that is used to decrypt and
a private key that's used to encrypt.  Unfortunately, Microsoft's RSA
built into System.Security.Cryptography is exactly the opposite of
that.

What I'm planning on being able to do is create a public key and attach
it to my assembly. and keep the private on my end.  Then I'm going to
use the private to encrypt licensing information and use the public to
decrypt it and check it against whatever.

Any help?