Calculation of Compound Interest in VB 2010 using Functions

Public Class Form1

Private Function CI(ByVal P As Single, ByVal R As Single, ByVal T As Single) As Double

        CI = (P * (1 + R / 100) ^ T) - P

End Function

Private Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click

        Dim CompInt As Single

        Dim Prin As Single

        Dim Rate As Single

        Dim Time As Single

        Prin = TextBox1.Text

        Rate = TextBox2.Text

        Time = TextBox3.Text

        CompInt = CI(Prin, Rate, Time)

        TextBox4.Text = Format(CompInt, "$#,##0.00")

End Sub

End Class