Use uma das 3 opções abaixo (3 construções lógicas diferentes)
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Versão 1
Option Explicit
Private Sub Worksheet_Change(ByVal Target As Range)
Const CHECK_COL = "M"
Dim tRow As Long, mVal As String
tRow = Target.Row
mVal = LCase(Me.Range(CHECK_COL & tRow).Value2)
Me.Rows(tRow).Hidden = (mVal = "validated")
End Sub
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Versão 2
Private Sub Worksheet_Change(ByVal Target As Range)
Const CHECK_COL = "M"
Dim tRow As Long, mVal As String
tRow = Target.Row
mVal = LCase(Me.Range(CHECK_COL & tRow).Value2)
Select Case mVal
Case "validated": Me.Rows(tRow).Hidden = True
Case "re-check": Me.Rows(tRow).Hidden = False
End Select
End Sub
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Versão 3
Private Sub Worksheet_Change(ByVal Target As Range)
Const CHECK_COL = "M"
Dim tRow As Long, mVal As String
tRow = Target.Row
mVal = LCase(Me.Range(CHECK_COL & tRow).Value2)
If mVal = "validated" Then
Me.Rows(tRow).Hidden = True
ElseIf mVal = "re-check" Then
Me.Rows(tRow).Hidden = False
End If
End Sub