Hello everyone,
I hope I am not too late to apologize. Unluckily yesterday I couldn't find the forum rules and couldn't think about explaining that I already opened a similar thread here:
Help with three dependent ActiveX comboboxes? (excelforum.com)

I did not mean to lack of respect to anyone. The fact is that I am not that expert in using forums and the need to receive help made me act without realizing I was actually breaking a rule.

I am sorry and I am willing to do whatever it takes to fix my mistake.