stop a countdown counting when date reached?

Hi

O3 = date added to list
P3 = waiting (yes/no)
Q3 = weeks waiting - has a formula that counts weeks waiting: =IF(O3="","",INT(((TODAY()-O3)/7)))
R3 = breach date - =IF(O3="","",INT((O3+42)))
S3 = date booked

Basically is there a formula/alter current formula so that the weeks waiting will automatically stop counting when the date booked date is reached?

Thanks