Private Sub btnConvert_Click()

    ' convert the RGB values to HSL using the formula from
    ' from https://www.niwa.nu/2013/05/math-behind-colorspace-conversions-rgb-hsl/

    Dim redColor As Double
    Dim greenColor As Double
    Dim blueColor As Double
    Dim min As Double
    Dim max As Double
    Dim luminanceValue As Double
    Dim saturationValue As Double
    Dim hueValue As Double

    ' convert to 0-1
    redColor = Format(Val(txtR.Text) / 255, "#.#0")
    greenColor = Format(Val(txtG.Text) / 255, "#.#0")
    blueColor = Format(Val(txtB.Text) / 255, "#.#0")

    ' find min and max of the three
    min = 2
    If redColor < min Then min = redColor
    If greenColor < min Then min = greenColor
    If blueColor < min Then min = blueColor

    max = 0
    If redColor > max Then max = redColor
    If greenColor > max Then max = greenColor
    If blueColor > max Then max = blueColor

    ' calculate lumanince value
    luminanceValue = Format((min + max) / 2, "#.#0")

    ' calculate saturation value
    If min = max Then
        saturationValue = 0
    Else
        If luminanceValue <= 0.5 Then
            saturationValue = (max - min) / (max + min)
        Else
            saturationValue = (max - min) / (2 - max - min)
        End If
        saturationValue = Format(saturationValue, "#.#0")
    End If

    ' calculate hue
    If redColor = max Then hueValue = (greenColor - blueColor) / (max - min)
    If greenColor = max Then hueValue = 2 + (blueColor - redColor) / (max - min)
    If blueColor = max Then hueValue = 4 + (redColor - greenColor) / (max - min)

    If (hueValue * 60) < 0 Then hueValue = (hueValue * 60) + 360 Else hueValue = (hueValue * 60)

    hueValue = Format(hueValue, "#.#0")
    txtH.Text = Format(hueValue, "###")
    txtS.Text = Format(saturationValue, "###%")
    txtL.Text = Format(luminanceValue, "###%")

End Sub

Private Sub txtB_Change()
    ChangeRGBColor
End Sub

Private Sub txtG_Change()
    ChangeRGBColor
End Sub

Private Sub txtR_Change()
    ChangeRGBColor
End Sub

Private Sub ChangeRGBColor()

    Dim redColor As Integer
    Dim greenColor As Integer
    Dim blueColor As Integer

    redColor = Val(txtR.Text)
    greenColor = Val(txtG.Text)
    blueColor = Val(txtB.Text)

    If redColor > 255 Then
        redColor = 255
        txtR.Text = redColor
    End If

    If greenColor > 255 Then
        greenColor = 255
        txtG.Text = greenColor
    End If

    If blueColor > 255 Then
        blueColor = 255
        txtB.Text = blueColor
    End If

    lblColor.BackColor = RGB(redColor, greenColor, blueColor)

End Sub