Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim age As Double = CDbl(txtAge.Text)
        Dim rest As Double = CDbl(txtRHR.Text)
        txtTHR.Text = CStr(THR(age, rest))

    End Sub
    Function THR(ByVal age As Double, ByVal rest As Double) As Double
        THR = Math.Round((((220 - age) - rest) * 0.6) + rest)
        Return THR
    End Function