' FB 1.05.0 Win64

Sub split (s As Const String, sepList As Const String, result() As String)
  If s = "" OrElse sepList = "" Then
     Redim result(0)
     result(0) = s
     Return
  End If
  Dim As Integer i, j, count = 0, empty = 0, length
  Dim As Integer position(Len(s) + 1)
  position(0) = 0

  For i = 0 To len(s) - 1
    For j = 0 to Len(sepList) - 1
      If s[i] = sepList[j] Then
        count += 1
        position(count) = i + 1
      End If
    Next j
  Next i

  Redim result(count)
  If count  = 0 Then
    result(0) = s
    Return
  End If

  position(count + 1) = len(s) + 1

  For i = 1 To count + 1
    length = position(i) - position(i - 1) - 1
    result(i - 1) = Mid(s, position(i - 1) + 1, length)
  Next
End Sub

Function expandRange(s As Const String) As String
  If s = "" Then Return ""
  Dim b() As String
  Dim c() As String
  Dim result As String = ""
  Dim As Integer start = 0, finish = 0, length
  split s, ",", b()
  For i As Integer = LBound(b) To UBound(b)
    split b(i), "-", c()
    length = UBound(c) - LBound(c) + 1
    If length = 1 Then
      start  = ValLng(c(LBound(c)))
      finish = start
    ElseIf length = 2 Then
       If Left(b(i), 1) = "-" Then
         start  = -ValLng(c(UBound(c)))
         finish = start
       Else
         start  = ValLng(c(LBound(c)))
         finish = ValLng(c(UBound(c)))
       End If
    ElseIf length = 3 Then
      start  = -ValLng(c(LBound(c) + 1))
      finish = ValLng(c(UBound(c)))
    Else
      start  = -ValLng(c(LBound(c) + 1))
      finish = -ValLng(c(UBound(c)))
    End If
    For j As Integer = start To finish
      result += Str(j) + ", "
    Next j
  Next i
  Return Left(result, Len(result) - 2) '' get rid of final ", "
End Function

Dim s As String = "-6,-3--1,3-5,7-11,14,15,17-20"
Print expandRange(s)
Print
Print "Press any key to quit"
Sleep