Sub Possibilities()
Dim sModel As String
Dim cl As Range
Dim rngModels As Range
Dim rngCatA As Range
Dim lClean As Long
Dim lColA As Long
Dim lColB As Long
Dim lColC As Long
Dim lColD As Long
With Worksheets("Sheet1")
'Range of model numbers to prepend
Set rngModels = .Range("A2:A3")
'First cell in data table
Set rngCatA = .Range("B8")
'Set up target list area
.Range("B16:B" & .Range("B" & .Rows.Count).End(xlUp).Row).ClearContents
.Range("B16").Value = "Model Number"
'Create possibilities
For Each cl In rngModels
For lColA = 0 To 3
For lColB = 0 To 3
For lColC = 0 To 3
For lColD = 0 To 3
'Generate raw possibilities
sModel = cl.Value & "/" & _
rngCatA.Offset(lColA, 0) & "/" & _
rngCatA.Offset(lColB, 1) & "/" & _
rngCatA.Offset(lColC, 2) & "/" & _
rngCatA.Offset(lColD, 3)
'Strip any instances of // (from blank quartets)
For lClean = 1 To 4
sModel = Replace(sModel, "//", "/")
Next lClean
'Remove trailing / if necessary (blank final quartet)
If Right(sModel, 1) = "/" Then sModel = Left(sModel, Len(sModel) - 1)
'Place value in cell
.Range("B" & .Range("B" & .Rows.Count).End(xlUp).Row).Offset(1, 0).Value = sModel
Next lColD
Next lColC
Next lColB
Next lColA
Next cl
End With
End Sub