Welcome to MrExcel - this code goes in the worksheet module of the sheet to be monitored for changes.
<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:#00007F">If</SPAN> Intersect(Target, [B:C]) <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:#00007F">With</SPAN> Application
.EnableEvents = <SPAN style="color:#00007F">False</SPAN>
.ScreenUpdating = <SPAN style="color:#00007F">False</SPAN>
<SPAN style="color:#00007F">End</SPAN> <SPAN style="color:#00007F">With</SPAN>
Range("D" & Target.Row & ":F" & Target.Row).Clear
<SPAN style="color:#007F00">' If C should be cleared on B, then</SPAN>
<SPAN style="color:#007F00">' range(target.offset(,1),target.offset(,3)).clear</SPAN>
<SPAN style="color:#00007F">With</SPAN> Application
.EnableEvents = <SPAN style="color:#00007F">True</SPAN>
.ScreenUpdating = <SPAN style="color:#00007F">True</SPAN>
<SPAN style="color:#00007F">End</SPAN> <SPAN style="color:#00007F">With</SPAN>
<SPAN style="color:#00007F">End</SPAN> <SPAN style="color:#00007F">Sub</SPAN>
</FONT>
It is currently set up to clear D:F, but alternative syntax for C:E/D:F included.