Ingresar en cuadro de texto solo numeros y signos

[David]

Coloca este código en el evento KeyPress del TextBox:

Código:

 
Dim Selected As Integer
If InStr("0123456789", Chr(KeyAscii)) = 0 Then
    If InStr("+-", Chr(KeyAscii)) <> 0 Then
        If Len(Text1) = 0 Then
            Text1 = Chr(KeyAscii)
        Else
            Dim Text As String
            Text = Text1
            Mid(Text, 1, 1) = Chr(KeyAscii)
            Text1 = Text
        End If
    End If
    If KeyAscii <> 8 Then KeyAscii = 0
Else
    If Len(Text1) > 0 Then
        Selected = Text1.SelStart
        Text1.Tag = Text1.Text
        Text1.Text = Left(Text1, Text1.SelStart) & Chr(KeyAscii) & Right(Text1, Len(Text1) - Text1.SelStart)
        Text1.Text = Left(Text1, 1) & Format(Right(Text1, Len(Text1) - 1), "#.00")
        If Right(Text1, 2) <> "00" And Right(Text1, 2) <> "25" And Right(Text1, 2) <> "50" And Right(Text1, 2) <> "75" Then
            Text1.Text = Text1.Tag
            Text1.SelStart = Selected
        Else
            Text1.SelStart = Selected + 1
        End If
    End If
    KeyAscii = 0
End If

Espero que te funcione...
Saludos