add some code to a website

i have a website where donations take place like this: there can be many admin accounts and this is set first, after user A registers, he will pay admin, user B registers and pays admin also. then User C and D will pay User A, and User E and F will pay B. that is the present function of the website. ***This is what I want: Now, as soon as user registers, i want user to pay 'gatekeeper', if the user selects 10000 package, user will pay 2000 to 'gatekeeper' if user selects 20000, user will pay 4000 to 'gatekeeper'. so, gatekeeper will regulate the users that registers and confirm them.*** after confirmation, site goes back to normal as described above. small project* need it in one hour max