De esta forma es muy lento?
Código [Seleccionar]
Private Function GetNumbers(sText As String) As String
Dim i As Integer
Dim sTmp As String
For i = 1 To Len(sText)
If IsNumeric(Mid$(sText, i, 1)) = True Then sTmp = sTmp & Mid$(sText, i, 1)
Next
GetNumbers = sTmp
End Function