This is to acknowledge your letter of (date)
You are definitely to be commended for your progress
during the past two months.
I do believe, however, that your recent request for a
raise is premature. I would suggest that it would be
more appropriate to discuss a salary increase after you
have worked here for six months. If you continue on
the same path, I am certain that your timely request
will be given careful consideration.
You are doing a fine job, keep up the good work!