Sure:
<font face=Courier New><SPAN style="color:#00007F">Private</SPAN> <SPAN style="color:#00007F">Sub</SPAN> Worksheet_Change(<SPAN style="color:#00007F">ByVal</SPAN> Target <SPAN style="color:#00007F">As</SPAN> Range)
<SPAN style="color:#007F00">' Code goes in the Worksheet specific module</SPAN>
<SPAN style="color:#00007F">Dim</SPAN> rng <SPAN style="color:#00007F">As</SPAN> Range
<SPAN style="color:#007F00">' Set Target Range</SPAN>
Set rng = Range("D:D")
<SPAN style="color:#007F00">' Only look at single cell changes</SPAN>
<SPAN style="color:#00007F">If</SPAN> Target.Count > 1 <SPAN style="color:#00007F">Then</SPAN> <SPAN style="color:#00007F">Exit</SPAN> <SPAN style="color:#00007F">Sub</SPAN>
<SPAN style="color:#007F00">' Only look at that range</SPAN>
<SPAN style="color:#00007F">If</SPAN> Intersect(Target, rng) <SPAN style="color:#00007F">Is</SPAN> <SPAN style="color:#00007F">Nothing</SPAN> <SPAN style="color:#00007F">Then</SPAN> <SPAN style="color:#00007F">Exit</SPAN> <SPAN style="color:#00007F">Sub</SPAN>
<SPAN style="color:#007F00">' Action if Condition(s) are met</SPAN>
ActiveSheet.Unprotect "PasswordHere"
Target.Locked = <SPAN style="color:#00007F">True</SPAN>
ActiveSheet.Protect "PasswordHere"
<SPAN style="color:#00007F">End</SPAN> <SPAN style="color:#00007F">Sub</SPAN></FONT>
Just make sure to unlock column D beforehand or you won't be able to make any entries to begin with...
HTH,
Smitty