excel - How to end infinite "change" loop in VBA

Question

I have a problem with visual basic. I want to make a macro/function that will multiply a number I enter by 3 and give a result in the same cell. I tried something like this:

Sub Worksheet_Change(ByVal Target As Range)
    If Target.Address = "$Q$21" Then
        Target.Value = Target.Value * 3
    End If
End Sub

but it doesn't work - I'm getting results like "xE25" because it keeps multiplying.

I'd like it to stop after first iteration or work only when I press "enter" not with every change in the cell.
It's quite easy to put a result in different cell, but it's not my point.


-----Edit:
I edited "If" line to :
If (Target.Column = 5 Or Target.Column = 11 Or Target.Column = 17 Or Target.Column = 23) And (Target.Row >= 19 And Target.Row <= 24) And Target.Value <> "" Then
so it would work on all cells that I need. After that, the best solution is the way given by @Chrismas007, because it doesn't prompt an error when trying to delete data in few cells at once.

Answer 1

With error handling to ensure .EnableEvents goes back to True:

Sub Worksheet_Change(ByVal Target As Range)
    On Error GoTo CleanExit
    If Target.Address = "$Q$21" Then
        Application.EnableEvents = False
        Target.Value = Target.Value * 3
    End If
CleanExit:
    Application.EnableEvents = True
    On Error GoTo 0
End Sub