You would have to wait to see if you passed Step 2 CK before you could even schedule Step 3. So there would be at least a few months between the two, if you consider 4-6 weeks to receive your score, then the waiting period to receive your scheduling permit.
From the NBME website:
"You must pass Step 1 and Step 2 before you are eligible to take Step 3. In LCME-accredited medical schools, although Step 1 and Step 2 can be taken in any order, most students will take Step 1 at the end of their second year and Step 2 in their fourth year; Step 3 is usually taken during the first or second year of postgraduate training."