Instead of what you're doing, if you track your Credit Card transactions in a proper Credit Card account, then you won't have difficulties like this, and many others mentioned here as a result of not using a Credit Card type account. A CC account functions just like a bank account, but is a type of liability instead of a type of asset.
To track a credit card account properly, set up a Credit Card type account on your chart of accounts. If you pay off your bill each month, then you don't need an opening balance. In this case, start with a 0.00 balance and enter all of the transactions in your new CC register since the last statement.
Once you do this, you can either enter your vendor payments as credit card charges, or you can actually pay your A/P bills using the credit card account using the Pay Bills feature, much as you might pay a bill using a check.
