Public Class Form1
    Private Sub BtnOblicz_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnOblicz.Click
        Dim Kwota As Single = CSng(TxtKapital.Text)
        Dim Procent As Single = CSng(TxtProcent.Text) / 100
        Dim KwotaK As Single = CSng(TxtKwotaKoncowa.Text)
        Dim Lata As Integer
        Lata = 0
        Do While Kwota < KwotaK
            Kwota = Kwota + Kwota * Procent
            Lata = Lata + 1
        Loop
        TxtLata.Text = Lata.ToString
    End Sub
End Class