Try this worksheet event macro:

Private Sub Worksheet_Calculate()

Set b9 = Range("B9")
Set a1 = Range("A1")

If b9.Value = 1 Then
   Application.EnableEvents = False
       b9.Locked = False
       a1.Locked = True
       ActiveSheet.Protect Contents:=True
   Application.EnableEvents = True
End If
End Sub

If the value of B9 becomes 1, then cell A1 becomes locked.

Because it is worksheet code, it is very easy to install and automatic to use:

1. right-click the tab name near the bottom of the Excel window
2. select View Code - this brings up a VBE window
3. paste the stuff in and close the VBE window

If you have any concerns, first try it on a trial worksheet.

If you save the workbook, the macro will be saved with it.

To remove the macro:

1. bring up the VBE windows as above
2. clear the code out
3. close the VBE window

To learn more about macros in general, see:

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

To learn more about Event Macros (worksheet code), see:

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

Hi,

Slightly more involved but try this. Select the cells you want this to work
for which in the case of my example are A1 - A10 and then
Format|cells|protection
remove the locked checkmark
Then
Tools Protection and protect the sheet with "mypass" as a passowrd (change
to suit but it must match the password in the code).

Right click the sheet tab, view code and paste this in and the first time
you enter xxx in a1 to A1 - A10 those cells also become protected.

Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Cells.Count > 1 Then Exit Sub
   If Not Intersect(Target, Range("A1:A10")) Is Nothing Then
       Application.EnableEvents = False
       If Target.Value = "xxx" Then
           ActiveSheet.Unprotect Password:="mypass"
           Target.Locked = True
           ActiveSheet.Protect Password:="mypass"
       End If
               Application.EnableEvents = True
       End If

End Sub

Mike

[language alert] what do you mean by "luck" the cell?