Ensure Cell Value Follows a Specified Character & Number Combination - vba

Question

Im new to vba I have a requirement where in I have restrict input to column A of a worksheet where user can only enter string in following format
'BATCH00_00' numbers can range from 0-99 I tried the below code but it does not work
Private Sub Worksheet_Change(ByVal Target As Range)
'PURPOSE: Checks a specific column and validates that value follow a specified pattern (numbers or letter combinations)
Dim cell As Range, rng As Range
Dim InvalidCount As Long, x As Long
x = 3 'Column to Validate
Set rng = ActiveSheet.UsedRange.Columns(x).Offset(1).Resize(ActiveSheet.UsedRange.Rows.Count - 1, 1)
For Each cell In rng.Cells
If Not UCase(cell.Value) Like "BATCH##_##Then
'Highlight Invalid Cell Yellow
msg "invalid entry please enter In following format BATCH00_00"
Next cell
End Sub
ALSO I have a another code on sheet which checks in column A there should not be any duplicate entries
Private Sub Worksheet_Change(ByVal Target As Range)
Dim rng As Range, r As Range, msg As String, x As Range
Set rng = Intersect(Columns(1), Target)
If Not rng Is Nothing Then
Application.EnableEvents = False
For Each r In rng
If Not IsEmpty(r.Value) Then
If Application.CountIf(Columns(1), r.Value) > 1 Then
msg = msg & vbLf & r.Address(0, 0) & vbTab & r.Value
If x Is Nothing Then
r.activate
Set x = r
Else
Set x = Union(x, r)
End If
End If
End If
Next
If Len(msg) Then
MsgBox "Duplicate values not allowed Invalid Entry" & msg
x.ClearContents
x.Select
End If
Set rng = Nothing
Set x = Nothing
Application.EnableEvents = True
End If
End Sub
how do I make the 1st code working & combine both to have one Private Sub Worksheet_Change

Answer 1

Try this (coments in code)
Private Sub Worksheet_Change(ByVal Target As Range)
Dim validationError Boolean
validationError = False
'if changed cell was not in A column, then exit sub
If Target.Column <> 1 Then Exit Sub
'check if format is valid BATCH00_00
If Not Target.Value Like "BATCH[0-9][0-9]_[0-9][0-9]" Then
MsgBox "Invalid format!"
validationError = True
Exit Sub
End If
'check for uniqueness in A column
If Application.WorksheetFunction.CountIf(Range("A:A"), Target.Value) > 1 Then
MsgBox "Values must be unique in A column!"
validationError = True
End If
If validationError Then
Application.EnableEvents = False
Target.Value = ""
Application.EnableEvents = True
End If
End Sub