Capture the final change in a Worksheet Change Event - vba

Question

In the worksheet(1), I have multiple plan-to-change cells, A1 and other cells, and others cells value depends on the the value of A1 as I set up the function(eg.,B1=A1+1). In this way, if I change the value of A1, other cells would change value as well, and the total changed cells would be the A1 plus others changed cells. However, as the quantity of "other cells" is quite large, when I run the following function in VBA:
Private Sub Worksheet_Change(ByVal Target As Range)
Cells(Target.Cells.Count, 21) = "ok"
End Sub
The column 21 would appear 3 "ok"s as I suppose because the large cells change happen in order, which actives three times the Worksheet_Change function. (the first ok for I change A1, the second for the time delay of updated function, the third for the final cell) However, I only want the Worksheet_Change to capture the final cells change after I change the value of A1, what should I do to avoid the previous capturing of Worksheet_Change function?

Answer 1

Modify your code to run only when A1 is changed.
Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Address = Range("A1").Address Then
Cells(1, 21).Value = "ok"
End If
End Sub

Answer 2

Target is often more than a single cell. Determine if one of the changed cells is A1 with Intersect and then only deal with A1.
If you plan to change a value on the same worksheet, shut down event handling temporarily so the Worksheet_Change does not try to run on top of itself.
Private Sub Worksheet_Change(ByVal Target As Range)
if not intersect(target, range("a1")) is nothing then
on error goto safe_exit
application.enableevents = false
dim trgt as range
for each trgt in intersect(target, range("a1"))
Cells(trgt.row, 21) = "ok"
next trgt
end if
safe_exit:
application.enableevents = true
End Sub
Since I don't believe that a1 is the actual target of your Target in your real world, I've made the code a little more verbose than it probably needs to be.