VBA Merge Help

Level II Help.jpg
Good Day! I am active duty military that runs construction projects for the Navy. I am currently in the process of automating a template while teaching myself VBA at the same time. The file I'm currently working lists my Project's Master Activities on the left and tracks them via 3 rows that have time estimated, time earned, and time expended. Those Columns fall under a bi-weekly reporting periods. Row 6 is the full date (5/9/2023 format) but uses the "ddd" display to show just the day. Rows 4 and 5 are =TEXT(G$6,"mmmm") and supposed to merge together to display the month. The goal is that the user can change G6s date, that trickles down the columns with a +14 days for the bi-weekly reporting. (that already works) then the VBA automatically unmerges G4:AF5 (a full year), autofills the range with =TEXT(G$6,"mmmm"), then it runs a merge code that should merge all similar valued cells together. However, where the code currently sits it only merges similar cells across rows 4 and 5, but does not merge G4:G5, or J4:L5 for November for example. I have tried running the merge code a second time but that runs into errors once added. Any help with this would be very much appreciated!
Code:

Private Sub Worksheet_Change(ByVal Target As Range)

Application.ScreenUpdating = False
Application.DisplayAlerts = False

If Target.Address = "$G$6" Then

Range("G4:AF5").Select
Selection.UnMerge
Selection.Borders(xlDiagonalDown).LineStyle = xlNone
Selection.Borders(xlDiagonalUp).LineStyle = xlNone
With Selection.Borders(xlEdgeLeft)
.LineStyle = xlContinuous
.ColorIndex = 0
.TintAndShade = 0
.Weight = xlMedium
End With
With Selection.Borders(xlEdgeTop)
.LineStyle = xlContinuous
.ColorIndex = 0
.TintAndShade = 0
.Weight = xlMedium
End With
With Selection.Borders(xlEdgeBottom)
.LineStyle = xlContinuous
.ColorIndex = 0
.TintAndShade = 0
.Weight = xlMedium
End With
With Selection.Borders(xlEdgeRight)
.LineStyle = xlContinuous
.ColorIndex = 0
.TintAndShade = 0
.Weight = xlMedium
End With
With Selection.Borders(xlInsideVertical)
.LineStyle = xlContinuous
.ColorIndex = 0
.TintAndShade = 0
.Weight = xlMedium
End With
Range("G4").Select
Selection.AutoFill Destination:=Range("G4:AF4"), Type:=xlFillDefault
Range("G4:AF4").Select
Range("G5").Select
Selection.AutoFill Destination:=Range("G5:AF5"), Type:=xlFillDefault
Range("G5:AF5").Select
End If

Dim rng As Range, cell As Range, mergedRange As Range
Set rng = Range("G4:AF5")

For Each cell In rng
If cell.Value <> "" And cell.Value = cell.Offset(0, 1).Value Then
If mergedRange Is Nothing Then
Set mergedRange = cell
End If
Set mergedRange = Union(mergedRange, cell.Offset(0, 1))
Else
If Not mergedRange Is Nothing Then
mergedRange.Merge
mergedRange.HorizontalAlignment = xlCenter
Set mergedRange = Nothing
End If
End If
Next cell

Application.DisplayAlerts = True
Application.ScreenUpdating = True

End Sub