VB.NET: IsNumeric using RegEX

[|2eM!x]

Thought I might post this bit of code in the same type thread

Private Function IsNumeric(ByVal Str As String) As Boolean
        Const Upper As Int32 = 57
        Const Lower As Int32 = 48
        For Each a As Char In Str
            Dim Base As Int16 = Convert.ToInt16(a)
            If (Base <= Upper And Base >= Lower) = False Then
                Return False
            End If
        Next
        Return True
    End Function