После некоторых исследований:
Function RetDigits(sIN As String) As String
Dim lookFor As String, v As String, ary
Dim i As Long, CH As String
lookFor = "1-"
RetDigits = ""
If InStr(sIN, lookFor) = 0 Then Exit Function
ary = Split(sIN, lookFor)
If Len(ary(1)) < 2 Then Exit Function
For i = 1 To 10
CH = Mid(ary(1), i, 1)
If IsNumeric(CH) Then
RetDigits = RetDigits & CH
End If
Next i
RetDigits = "1-" & RetDigits
End Function