Continuing education with a full-time job?

I would really like to get my oncology nursing certificate, however, that would involve taking a 3 month field placement at the end of the program. My question to you is, how do I do this with a full-time job? For those who have done it - did you take a leave of absence to complete the clinical component or is there is another way? FYI the other five courses are online and all of the course components need to be completed within 5 years to receive a certificate.