How to show " Sub Category List " of " Main Category List " ?

Hello Every One!

I have got a UserForm with Two ComboBoxes and One TextBox.

ComboBox1 which is name as " Select Main Category " . Here are three options which are " Rent, Bill, Other".
ComboBox2 which is name as " Select Sub Category ".
TextBox1 which is name as " Other ".

I want when user select " Rent " from Main Category ComboBox then in Sub Category ComboBox it should show only these two options " House Rent " and " Office Rent " and it should locked " Other " textbox.

If user select " Bill " from Main Category ComboBox then in Sub Category ComboBox it should show only these two options " Electricity Bill" and "Gas Bill" and it should locked " Other " textbox.

If user select " Other " from Main Category ComboBox then it should locked Sub Category ComboBox and unlock " Other " Text Box to allow user to write here manually.

I have Attached UserForm.

I hope you guys will be understanding what I really mean.

Please help I would be really thankful to you.

Regards
z-eighty2