Selection, valeur Min, puis copie autre feuille

Sub Filling_B()
    Dim k As Long
    Dim LastlineIn As Integer, LastlineOut As Integer
    Dim Mini As Integer
    Dim Plage As Range

    With Worksheets("INPUT")
        Lastline = .Range("A" & Rows.Count).End(xlUp).Row 'Compter le nombre de lignes'
        For k = 3 To Lastline Step 2                  'faire varier de 3 à la dernière ligne'
            Set Plage = .Range("B" & k & ":B" & k + 1) 'mettre "Bk" et "Bk+1" dans Range'
            Mini = Application.WorksheetFunction.Min(Plage)  'mettre le min de Range dans Min'
            LastlineOut = Worksheets("OUTPUT").Range("C" & Rows.Count).End(xlUp).Row + 1
            Worksheets("OUTPUT").Range("C" & LastlineOut) = Mini
        Next k
    End With

End Sub

Sub Filling_B_bis()
    Dim k As Long
    Dim LastlineIn As Integer, LastlineOut As Integer
    Dim Min As Integer, V1 As String, V2 As String
    Dim Plage As Range

    With Worksheets("INPUT")
        Lastline = .Range("A" & Rows.Count).End(xlUp).Row
        For k = 3 To Lastline Step 2
            V1 = Range("B" & k).Value
            V2 = Range("B" & k + 1).Value
            If V1 < V2 Then V1 = Min Else V2 = Min
            LastlineOut = Worksheets("OUTPUT").Range("C" & Rows.Count).End(xlUp).Row + 1
            Worksheets("OUTPUT").Range("C" & LastlineOut) = Mini
        Next k
    End With

End Sub

Sub Filling_B_bis()

    Dim K As Integer
    Dim Lastline As Integer
    Dim Min As String
    Dim V1 As String, V2 As String
    

    Set shJT = ActiveWorkbook.Sheets("INPUT")

    Lastline = Range("A" & Rows.Count).End(xlUp).Row
    
    For K = 3 To Lastline Step 2
        Set shJT = ActiveWorkbook.Sheets("INPUT")
        
        V1 = Range("B" & K).Value
        V2 = Range("B" & K + 1).Value
        If V1 < V2 Then Min = V1 Else Min = V2

        Set shJT = ActiveWorkbook.Sheets("OUTPUT")
        LastlineOut = Worksheets("OUTPUT").Range("C" & Rows.Count).End(xlUp).Row + 1
        Worksheets("OUTPUT").Range("C" & LastlineOut) = Min

    Next K

End Sub

Sub Filling_B_Min()

    Dim K As Integer
    Dim Lastline As Integer
    Dim Min As String
    Dim V1 As String, V2 As String
    Application.ScreenUpdating = False
      
    

    Sheets("INPUT").Select

    Lastline = Range("A" & Rows.Count).End(xlUp).Row
    
    For K = 3 To Lastline Step 2
        Sheets("INPUT").Select
        
        V1 = Range("B" & K).Value
        V2 = Range("B" & K + 1).Value
        If V1 < V2 Then Min = V1 Else Min = V2

        Sheets("OUTPUT").Select
        LastlineOut = Worksheets("OUTPUT").Range("C" & Rows.Count).End(xlUp).Row + 1
        Worksheets("OUTPUT").Range("C" & LastlineOut) = Min

    Next K
    Application.ScreenUpdating = True

End Sub

Option Explicit
Option Base 1

Sub filling_B()
Dim LastlineIn As Integer, T_in(), Nbre As Integer, Idx_in As Integer
Dim T_out(), idx_out As Integer

Application.ScreenUpdating = False 'fige le défilement de l'écran
With Sheets("input")
     LastlineIn = .Range("B" & Rows.Count).End(xlUp).Row 'Compter le nombre de lignes'
     T_in = Application.Transpose(.Range("B3:B" & LastlineIn))
End With

Nbre = UBound(T_in)
If Nbre Mod 2 <> 0 Then Nbre = Nbre - 1 'ajuste au nombre d'éléments pair
 'collecte les mini
ReDim T_out(Nbre / 2) 'dimensionne le tableau des mIn
idx_out = 1
For Idx_in = 1 To Nbre Step 2
     T_out(idx_out) = T_in(Idx_in)
     If T_in(Idx_in) >= T_in(Idx_in + 1) Then T_out(idx_out) = T_in(Idx_in + 1)
      idx_out = idx_out + 1
Next
'restitution
With Sheets("output")
     .Range("C1:C18000").Clear
     With .Range("C1").Resize(UBound(T_out), 1)
          .Value = Application.Transpose(T_out)
          .Borders.Weight = xlThin
     End With
     .Activate
End With
End Sub