Conversion Hexadecimal to RGB value VBA Macro

Hello,
I am a student and for a project I need to to adapt the look and feel of my application. To do this, I would first have to analyse some code and enter the colour values in order in an Excel table.
For this I need a column with the hex value of the colour contained in the source code file, the RGB value and a third column that is coloured in the corresponding colour. If the hex or RGB value is changed, the third cell should be changed accordingly. Additionally, a column with the name of the function in which the colour is set.

I enclose here the draft of my work on it.
Today I can convert either from HEX to RGB or RGB to Hex with the help of excel formulas. I tried to convert from rgb to hex with a macro but it doesn´t work.

Can you please help me