XL 2016 Sélectionner les cellules contenant deux suites de lettres

Sub SelectMONDET()
    Dim Selection As Range
    Dim Cell As Range
    Const NbColonnesSelection = 9   'A adapter selon le nombre de colonnes à sélectionner
 
    For Each Cell In Intersect(ActiveSheet.UsedRange, ActiveSheet.Columns(ActiveSheet.UsedRange.Column))
        If VarType(Cell) = vbString Then
            If Left(Cell.Value, 3) = "MON" _
            Or Left(Cell.Value, 3) = "DET" _
            Then
                If Selection Is Nothing _
                Then Set Selection = Cell.Resize(1, NbColonnesSelection) _
                Else Set Selection = Union(Selection, Cell.Resize(1, NbColonnesSelection))
            End If
        End If
    Next Cell
 
    If Not Selection Is Nothing Then Selection.Select
End Sub

Sub DefinirPlage()
Dim crit1$, crit2, ncol%, c As Range, P As Range, tablo, i&, x$, deb As Range, fin As Range, Plage As Range
crit1 = "DET" 'à adapter
crit2 = "MON" 'à adapter
ncol = 9 'à adapter
Set c = Cells.Find(crit1, , xlValues, xlPart)
If c Is Nothing Then Set c = Cells.Find(crit2)
If c Is Nothing Then Exit Sub
Set P = Intersect(c.EntireColumn, ActiveSheet.UsedRange)
tablo = P.Resize(P.Rows.Count + 1) 'matrice, plus rapide, au moins 2 éléments
For i = 1 To UBound(tablo) - 1
    x = CStr(tablo(i, 1))
    If InStr(x, crit1) + InStr(x, crit2) Then Set deb = P(i): Exit For
Next
If deb Is Nothing Then Exit Sub
For i = UBound(tablo) - 1 To 1 Step -1
    x = CStr(tablo(i, 1))
    If InStr(x, crit1) + InStr(x, crit2) Then Set fin = P(i): Exit For
Next
Set Plage = Range(deb, fin).Resize(, ncol)
'---suite du code en utilisant Plage---
Plage.Select 'mais en VBA il est recommandé de ne pas sélectionner...
End Sub