Dim text As String = "1,2,3,4,5,1,2,3,4,5,1,2,3,4,5,1,2,3,4,5"
 
Dim parts() As String = Text.Split(","c)
Dim sums(4) As Integer
 
For i As Integer = 0 To 4
   For k As Integer = i To parts.Length - 1 Step 5
       sums(i) += CInt(parts(k).Trim)
   Next k
Next i
 
Dim stb As New System.Text.StringBuilder
For i As Integer = 0 To 4
   stb.Append(CStr(sums(i)) + ", ")
Next i
 
text = stb.ToString