Conversation so far:
What was Raymond Berry's first coaching job ?
After retiring from playing, Berry joined Tom Landry's Dallas Cowboys coaching staff.
What year did he joined Dallas Cowboys ?
In 1970, after two seasons, Berry took a job with Frank Broyles.
How many years did he work for Frank Broyles ?
In 1973 Berry joined Don McCafferty.
How long did he stayed with Don McCafferty ?
In 1976, Berry joined former SMU teammate Forrest Gregg.

Question: For how long did he work with Forrest Gregg ?
Self-contained rewrite: For how long did Raymond Berry work with Forrest Gregg ?