How to extract a number from alphanumeric text string?

Dim mystring, myLength
mystring = "abhikansh567st1239test"
myLength = Len(mystring)

For i = 1 To myLength
    If Asc(Mid(mystring, i, 1)) <> 32 Then
        If Asc(Mid(mystring, i, 1)) >= 48 And Asc(Mid(mystring, i, 1)) <= 57 Then
            myNumber = myNumber & Mid(mystring, i, 1)
        End If
    Else
        msgbox("no numeric")
    End If
Next
msgbox(myNumber)