security when processing credit cards

Here's what I plan on doing. Please let me know if this is secure.

On a site with a secure layer I will be getting a credit card number. Then in asp I will encode the number and put the encoded number in a acess database. The administrater will be able to go in a passworded page and retrieve the credit card number (Which will be decoded in the process) to manually bill.
Is this secure?

nope.

A) nothings is 'secure'
B) you haven't mentioned anything about your box's security, so no one can really answer this question
C) if you can decrypt it, especially if the box is compromised, they have the decryption key right there, so there's really no point if they have that.