I have an input range where I can have up to 10 rows containing data, and this is repeated on up to 10 columns. so maximum input cells is 10x10 = 100. What I'm trying to do, is generate a list, of all possible combinations when picking one item from each of the available columns. I have this example macro that seems quite neat, but it doesn't quite work and I can't work out why. I'm looking for some help to either identify the error in this code, or show me a more efficient way to do this. I initially tried with a series of nested loops, but the changing number of columns got me stumped!

Thanks! Nick

Example code:

VBA Code:

```
Sub ListCombinations()
Dim col As New Collection
Dim c As Range, sht As Worksheet, res
Dim i As Long, arr, numCols As Long
Set sht = ActiveSheet
For Each c In sht.Range("A1:J1").Cells
col.Add Application.Transpose(sht.Range(c, c.End(xlDown)))
numCols = numCols + 1
Next c
res = Combine(col, "~~")
For i = 0 To UBound(res)
arr = Split(res(i), "~~")
sht.Range("H1").Offset(i, 0).Resize(1, numCols) = arr
Next i
End Sub
'create combinations from a collection of string arrays
Function Combine(col As Collection, SEP As String) As String()
Dim rv() As String
Dim pos() As Long, lengths() As Long, lbs() As Long, ubs() As Long
Dim t As Long, i As Long, n As Long, ub As Long
Dim numIn As Long, s As String, r As Long
numIn = col.Count
ReDim pos(1 To numIn)
ReDim lbs(1 To numIn)
ReDim ubs(1 To numIn)
ReDim lengths(1 To numIn)
t = 0
For i = 1 To numIn 'calculate # of combinations, and cache bounds/lengths
lbs(i) = LBound(col(i))
ubs(i) = UBound(col(i))
lengths(i) = (ubs(i) - lbs(i)) + 1
pos(i) = lbs(i)
t = IIf(t = 0, lengths(i), t * lengths(i))
Next i
ReDim rv(0 To t - 1) 'resize destination array
For n = 0 To (t - 1)
s = ""
For i = 1 To numIn
s = s & IIf(Len(s) > 0, SEP, "") & col(i)(pos(i)) 'build the string
Next i
rv(n) = s
For i = numIn To 1 Step -1
If pos(i) <> ubs(i) Then 'Not done all of this array yet...
pos(i) = pos(i) + 1 'Increment array index
For r = i + 1 To numIn 'Reset all the indexes
pos(r) = lbs(r) ' of the later arrays
Next r
Exit For
End If
Next i
Next n
Combine = rv
End Function
```