Moon Phases.

http://www.ameritech.net/users/paulcarlisle/MoonCalendar.html

http://imagiware.com/astro/moon.cgi

Lots of other sites readily available.

hi!
here's am approxiamtion of the moon phase
0..3 is new moon.
4..7 full moon.
try this. not fully tested.
but please give me feed back .ok

<font face=Courier New><SPAN style="color:#00007F">Function</SPAN> Moon_Phase(y, m, d) <SPAN style="color:#00007F">As</SPAN> <SPAN style="color:#00007F">Integer</SPAN>
    <SPAN style="color:#00007F">If</SPAN> m < 3 <SPAN style="color:#00007F">Then</SPAN>
        y = y - 1
        m = m + 12
    <SPAN style="color:#00007F">End</SPAN> <SPAN style="color:#00007F">If</SPAN>
    m = m + m
    c = 365.25 * y
    e = 30.6 * m
    jd = c + e + d - 694039.09
    jd = jd / 29.53
    b = Int(jd)
    jd = jd - b
    b = Int(jd * 8 + 0.5)
    <SPAN style="color:#00007F">If</SPAN> b = 8 <SPAN style="color:#00007F">Then</SPAN> b = 0
    Moon_Phase = b
<SPAN style="color:#00007F">End</SPAN> <SPAN style="color:#00007F">Function</SPAN></FONT>

http://www.xylem.f2s.com/kepler/astrofnc.html

Not sure if your answer is there but there's a hell of a lot of UDF's for astronomical functions!