Frank:
You need to clarify for us if you were thinking of using a hardware I2C controller on your microcontroller or if you were going to bit-bang the interface.

Also please note that you should read up on how I2C actually works. It uses two open drain lines that operate bi-directionally. It will be nearly impossible to change the way that an on-board hardware I2C peripheral works.

From the nature of the question that you posted it sounds to me like you should either make yourself a custom bit-banged implementation (like has already been suggested) or look at using an on-board SPI type interface.

Michael Karas