Woudl this solve your problem?:
Code:
    Private Sub TextBox1_LostFocus(ByVal sender As Object, ByVal e As System.EventArgs) Handles TextBox1.LostFocus
        TextBox1.Text = Format(Math.Round(CDec(TextBox1.Text), 2), "Currency")
    End Sub
It would round to two decimal places and format it as currency when the user moved to another box. This way it doesnt matter if they type in the decimal or not.

Allan.