Something like this:

Sub StripNonNumerics()
Dim oRng As Range
Dim oChar As Range
Dim tempString As String
Set oRng = Selection.Range

For Each oChar In oRng.Characters
 If Asc(oChar) > 47 And Asc(oChar) < 58 Then
   tempString = tempString + oChar
 End If
Next
Selection.Range = tempString
End Sub

Lucas,

I didn't do a very good job with my first reply.  You want to strip
nonnumerics from a string not a range.  Try:

Sub StripNonNumericsFromString()
Dim oString As String
Dim i As Long
Dim cleanString As String
oString = "abc123efg"
For i = 1 To Len(oString)
 If Asc(Mid(oString, i, 1)) > 47 And Asc(Mid(oString, i, 1)) < 58 Then
   cleanString = cleanString + (Mid(oString, i, 1))
 End If
Next
MsgBox cleanString
End Sub