One way:

put this in your worksheet code module (right-click the worksheet tab
and choose "View Code"):

Private Sub Worksheet_Change(ByVal Target As Excel.Range)
With Target
If Not Intersect(.Cells, Range("A1")) Is Nothing Then
Application.EnableEvents = False
.Value = .Value / 86400
.NumberFormat = "[m]"
Application.EnableEvents = True
End If
End With
End Sub

If you're not familiar with macros, see David McRitchie's "Getting
Started with Macros":

http://www.mvps.org/dmcritchie/excel/getstarted.htm

In article ,
"XOXO" wrote:

Thanks JE, I did a custom format [mm] but I still need to enter 0:0:478 and
on the cell I get 7 which is good. But is there a way where I can enter the
478 and get 7 in return. Will the macro be able to do this.