Add Days to date, but alter date to Friday when it falls on Sat or Sun

I have created an excel sheet that calculates a client's lab draws dates, based on a initial date that is manually entered. 30 days is added to the initial date, and so on to compute the next 11 dates for lab draws, for a total of 12 dates listed. This is then used to generate a letter in word that can be sent to the client.

My dilemma: I want to count all days Mon-Sun in the 30 days; however I want the dates that fall on sat and sun to revert to the preceding Friday. For example if the date is 2/26/11, or 2/27/11, I want it to list the date 2/25/11. Optimally it should then go 30 days from that date to compute the next one. I have used a simple formula for the initial computation.

=IF(C2="","",C2+30)

I am a self taught basic excel user, so please be gentle =).
thanks