Well.. look into the %date% variable. This doesn't give a mmddyy format, but you might be able to modify it. You could use the echo command and output operators (> for truncating or >> for appending) for the file. Example:
echo mms://hostname/%date%/ >> %date%.strm
Of course, this would pose the problem of illegal characters in a filename ('/'), so you'd have to find a way to modify the data given from the %date% variable.
Good luck.