sp = Split(ActiveCell.Value, ",")     
If UBound(sp) > 0 Then ActiveCell.Offset(0, 1) = Val(sp(0)) + Val(sp(1))

Function ss(a)
     ss = Evaluate(Replace(a, ",", "+"))
End Function

=AtREGEX("1,2";"\d+";-2)

Public Function ATREGEX(ByRef text As Variant, _
                         ByRef pattern As Variant, _
                         Optional ByVal num_submatch As Long = -10, _
                         Optional ByRef new_text As Variant = "", _
                         Optional ByVal is_ignoreCase As Boolean = True, _
                         Optional ByVal is_global As Boolean = True) As Variant

Dim objRegex
Dim colMatch
Dim sMatchString As String
Dim sSumMatch As Double
Dim i As Integer

On Error GoTo err_

ATREGEX = ""

Set objRegex = CreateObject("vbscript.regexp")

With objRegex
     .Global = is_global
     .IgnoreCase = is_ignoreCase
     .pattern = pattern
End With

If num_submatch >= -9 Then
     Set colMatch = objRegex.Execute(text)
      
     If num_submatch = -1 Then
         ATREGEX = colMatch.Count
         Exit Function
     End If
      
     If num_submatch = -2 Then
         sSumMatch = 0
         For i = 0 To colMatch.Count - 1
             sSumMatch = sSumMatch + CDbl(colMatch(i).Value)
         Next
         ATREGEX = sSumMatch
         Exit Function
     End If
      
     If colMatch.Count = 0 Then
         ATREGEX = ""
     Else
         If num_submatch = 0 Then
             sMatchString = ""
             For i = 0 To colMatch.Count - 1
                 sMatchString = sMatchString + CStr(colMatch(i).Value) + ","
             Next
             ATREGEX = Left(sMatchString, Len(sMatchString) - 1)
         Else
             ATREGEX = colMatch(num_submatch - 1)
         End If
     End If
Else
     ATREGEX = objRegex.Replace(text, new_text)
End If

err_:
End Function