Check if two cells match specific values to create MsgBox - excel

Question

I am trying to check if two cells have two different values. I want to create a MsgBox for when if cell A1 is A and B1 is B to create MsgBox with text. But that the MsgBox will only pop up once.
The code works when I have one cell:
Option Explicit
Dim oldVal
Private Sub Worksheet_Change(ByVal Target As Range)
If (Target.Address = "$A$1") Then
If Target.Value = "A" And Target.Value <> oldVal Then
oldVal = Target.Value
MsgBox "Text."
End If
End If
End Sub
But I get error message when I try to for two cells:
Compile error: Procedure declaration does not match description of
event or procedure having the same name.
Option Explicit
Dim oldVal
Dim oldVal2
Private Sub Worksheet_Change(ByVal Target1 As Range, ByVal Target2 As Range)
If (Target1.Address = "$A$1") And (Target2.Address = "$B$1") Then
If Target1.Value = "A" And Target2.Value = "B" And Target1.Value <> oldVal And Target2.Value <> oldVal2 Then
oldVal = Target1.Value
oldVal2 = Target2.Value
MsgBox "Text."
End If
End If
End Sub
What can I do?

Answer 1

First of all you cannot change the parameters of the Worksheet.Change event and add more than one Target like this:
Private Sub Worksheet_Change(ByVal Target1 As Range, ByVal Target2 As Range)
'this does not work!
Instead you need to check if the Target intersects (Application.Intersect method) with your desired range and then check the values of A1 and B1.
Option Explicit
Private Sub Worksheet_Change(ByVal Target As Range)
If Not Intersect(Target, Me.Range("A1,B1")) Is Nothing Then 'check if A1 or B1 changed
If Me.Range("A1").Value = "A" And Me.Range("B1").Value = "B" Then
MsgBox "A1=A and B1=B"
End If
End If
End Sub