Sub test()
    FillRight Range("P26"), 3
    FillLeft Range("P26"), 6
    FillDown Range("P26"), 12
    FillUp Range("P26"), 4
End Sub

Sub FillRight(rr As Range, nn As Long)
    Dim arr As Variant
    ReDim arr(1 To nn)
    Dim yy As Long
    For yy = 1 To nn
        arr(yy) = yy
    Next
    rr.Resize(1, UBound(arr)) = arr
End Sub
Sub FillLeft(rr As Range, nn As Long)
    Dim arr As Variant
    ReDim arr(1 To nn)
    Dim yy As Long
    For yy = 1 To nn
        arr(yy) = nn - yy + 1
    Next
    rr.Offset(0, -nn + 1).Resize(1, UBound(arr)) = arr
End Sub
Sub FillDown(rr As Range, nn As Long)
    Dim arr As Variant
    ReDim arr(1 To nn, 1 To 1)
    Dim yy As Long
    For yy = 1 To nn
        arr(yy, 1) = yy
    Next
    rr.Resize(UBound(arr, 1), 1) = arr
End Sub
Sub FillUp(rr As Range, nn As Long)
    Dim arr As Variant
    ReDim arr(1 To nn, 1 To 1)
    Dim yy As Long
    For yy = 1 To nn
        arr(yy, 1) = nn - yy + 1
    Next
    rr.Offset(-nn + 1, 0).Resize(UBound(arr, 1), 1) = arr
End Sub