Limites de la boucle "For...Next" VBA

Sub seqp1()
Dim i As Long
Dim k As Long
Application.Calculation = xlCalculationManual
Application.ScreenUpdating = False
For i = 1 To Range("B65536").End(xlUp).Row
    If Cells(i, 2).Value = "?" Then
        Cells(i + 1, 2).Value = Cells(i, 3).Value
    End If
    
For k = 1 To Range("B65536").End(xlUp).Row
    If Cells(i + k, 2).Value <> "?" And Cells(i + k, 2).Value <> "" Then
        Cells(i + k, 2).Value = Cells(i + 1, 2).Value
    Else
Exit For
End If
Next k
Next i
Application.ScreenUpdating = True
Application.Calculation = xlCalculationAutomatic
End Sub

Dim t As Variant, t2() As Variant, x As Long, i As Long, z As Integer, k As Long
Sub es()
On Error Resume Next
Application.ScreenUpdating = False
t = Range("a1:f" & Range("a65536").End(xlUp).Row)
x = 1: z = 1
For i = 1 To UBound(t)
If t(i, 2) <> "?" Then t(i, 2) = t(i - z, 3): z = z + 1 Else z = 1
ReDim Preserve t2(1 To 6, 1 To x)
For k = 1 To 6
t2(k, x) = t(i, k): Next k: x = x + 1: Next i
Range("A1:f65536").ClearContents
Range("a1").Resize(UBound(t2, 2), UBound(t2, 1)) = Application.Transpose(t2)
Erase t, t2
End Sub

Sub es()
On Error Resume Next
Application.ScreenUpdating = False
t = Range("b1:c" & Range("b65536").End(xlUp).Row)
x = 1: z = 1
For i = 1 To UBound(t)
If t(i, 1) <> "?" Then t(i, 1) = t(i - z, 2): z = z + 1 Else z = 1
ReDim Preserve t2(1 To 2, 1 To x)
For k = 1 To 2
t2(k, x) = t(i, k): Next k: x = x + 1: Next i
Range("b1:c65536").ClearContents
Range("b1").Resize(UBound(t2, 2), UBound(t2, 1)) = Application.Transpose(t2)
Erase t, t2
End Sub

Sub seqp1()
Dim Seq

Application.ScreenUpdating = False
For Each cel In Range("B1:B" & Range("B65536").End(xlUp).Row)
  If cel.Value = "?" Then
    Seq = Cells(cel.Row, 3)
    Else
    cel.Value = Seq
  End If
Next
Application.ScreenUpdating = True
End Sub

Sub seq1()
    Application.ScreenUpdating = False
        Range("IU1").Value = "?"
        Range("IV1").Value = 10
        Range("IU2").FormulaR1C1 = "=IF(RC2=""?"",""?"",IF(R[-1]C=""?"",R[-1]C[1],R[-1]C))"
        Range("IV2").FormulaR1C1 = "=R[-1]C+10"
        
        With Range("IU2:IV" & Range("A65536").End(xlUp).Row)
            .FillDown
            If Application.Calculation <> xlCalculationAutomatic Then .Calculate
        End With
        
        Range("IU1:IV" & Range("A65536").End(xlUp).Row).Copy
        Range("B1").PasteSpecial xlPasteValues
        
        Columns("IU:IV").ClearContents
    Application.ScreenUpdating = True
End Sub

Sub es()
Dim t As Variant, t2() As Variant, x As Long, i As Long, z As Long, k As Long
On Error Resume Next
Application.ScreenUpdating = False
t = Range("b1:b" & Cells(Rows.Count, 2).End(xlUp).Row)
x = 1: z = 1
For i = 1 To UBound(t)
If t(i, 1) <> "?" Then t(i, 1) = Cells(i - z, 3): z = z + 1 Else z = 1
ReDim Preserve t2(1 To 1, 1 To x)
For k = 1 To 1
t2(k, x) = t(i, k): Next k: x = x + 1: Next i
Columns("b:b").ClearContents
Range("b1").Resize(UBound(t2, 2), UBound(t2, 1)) = Application.Transpose(t2)
Erase t, t2
End Sub