Public Function Faktorial(ByVal nilai As Byte) As Double
        Dim hasil As Double = 1
        For i = 2 To nilai
            hasil = hasil * i
        Next
        Faktorial = hasil
    End Function

Public Function Kombinasi(ByVal a As Long, ByVal b As Integer) As Double
        Kombinasi = Faktorial(a) / (Faktorial(a - b) * b)
    End Function

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
       Dim  c As Double
       c = Kombinasi(TextBox1.Text, TextBox2.Text)
        Label1.Text = c
    End Sub