Writing to multiple cells using If Target.Address = " " Then - vba

Question

I have basic code that allows the values written to this cell to be summed while maintaining the cumulative value. So if I were to type "4" into the cell, and then type "10" into the cell, the result would be "14" (not just the second value entered of "10"). Here is what I have and I must say that it works.
#
Option Explicit
Dim oldvalue As Double
Private Sub Worksheet_Change(ByVal Target As Excel.Range)
If Target.Address = "$J$5" Then
On Error GoTo fixit
Application.EnableEvents = False
If Target.Value = 0 Then oldvalue = 0
Target.Value = 1 * Target.Value + oldvalue
oldvalue = Target.Value
fixit:
Application.EnableEvents = True
End If
End Sub
#
However, I want to apply this treatment to more than just cell J5. Say for example, I want the same code logic applied to cell R5 as well.
Thur far I have tried using
OR
and I have also tried using
If Not Intersect (Target, Range("J5:R5")) Is Nothing Then
But each of these approaches ties the two cells together (so that what I enter into one gets summed into both - each cell is summing values added to the other). I can't figure it out to save my life, so took to this forum in the hopes of finding someone smarter than me.

Answer 1

Maybe (this is assuming existing logic is correct....not sure why you set old value to 0 if Target = 0 and what value the *1 adds?)
Option Explicit
Dim oldvalueJ As Double
Dim oldValueR As Double
Private Sub Worksheet_Change(ByVal Target As Excel.Range)
On Error GoTo fixit
Application.EnableEvents = False
Select Case Target.Address
Case "$J$5"
If Target = 0 Then oldvalueJ = 0
Target = Target + oldvalueJ
oldvalueJ = Target
Case "$R$5"
If Target = 0 Then oldValueR = 0
Target = Target + oldValueR
oldValueR = Target
End Select
fixit:
Application.EnableEvents = True
End Sub

Answer 2

This is a bit more dynamic by allowing you to add unlimited cells; it also validates user input
Standard Module
Option Explicit 'Generic Module
Public Const WS1_MEM_RNG = "C5,J5,R5" 'Sheet1 memory cells
Public prevWs1Vals As Object
Public Sub SetPreviousWS1Vals()
Dim c As Range
For Each c In Sheet1.Range(WS1_MEM_RNG).Cells
If Len(c.Value2) > 0 Then prevWs1Vals(c.Address) = c.Value2
Next
End Sub
Sheet1 Module
Option Explicit 'Sheet1 Module
Private Sub Worksheet_Change(ByVal Target As Excel.Range)
If Target.CountLarge = 1 Then
If Not Intersect(Target, Me.Range(WS1_MEM_RNG)) Is Nothing Then GetPrevious Target
End If
End Sub
Private Sub GetPrevious(ByVal cel As Range)
Dim adr As String: adr = cel.Address
Application.EnableEvents = False
If Not IsError(cel.Value) And IsNumeric(cel.Value2) And Not IsNull(cel.Value) Then
If IsDate(cel.Value) Then
cel.NumberFormat = "General"
cel.Value2 = prevWs1Vals(adr)
Else
If cel.Value2 = 0 Then prevWs1Vals(adr) = 0
cel.Value2 = cel.Value2 + prevWs1Vals(adr)
prevWs1Vals(adr) = cel.Value2
End If
Else
cel.Value2 = prevWs1Vals(adr)
End If
Application.EnableEvents = True
End Sub
ThisWorkbook Module
Option Explicit 'ThisWorkbook Module
Private Sub Workbook_Open()
If prevWs1Vals Is Nothing Then Set prevWs1Vals = CreateObject("Scripting.Dictionary")
SetPreviousWS1Vals
End Sub
It can also enforce positives only

Answer 3

use commas to separate ranges, and add a Worksheet_SelectionChange() event to record the last user selected cell
Option Explicit
Dim oldvalue As String
Private Sub Worksheet_Change(ByVal Target As Excel.Range)
If Intersect(Target, Range("J5,R5")) Is Nothing Then Exit Sub
If Target.Value = 0 Then Exit Sub
On Error GoTo fixit
Application.EnableEvents = False
Target.Value = Target.Value + oldvalue
fixit:
Application.EnableEvents = True
End Sub
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
If Target.CountLarge = 1 Then oldvalue = Target.Value
End Sub