Write some Software

I've a tourism website with online booking system working under Joomla 3.2 (English), what I need is to create a custom code - Specific booking application, the idea is to allow the user to select [login to view URL] of trip days , based on this he would select 2. The places that He would like to go to [login to view URL] will be presented with Initial Trip cost according to his selection if he is the only participant, and he will be presented with the cost if another two persons join the trip (3 with him), and the cost if 6 persons join the trip with him (total of 7) - Input box for number of participants is by default 1, but the user can change and choose the number of participants with him. The system would recalculate the cost according to number of participants 4. The user would choose the trip date. 5. User Registration box will appear (User name, Email Address, Nationality, Gender & Age & Password ) 6. User would be prompted with two actions that will took place once he click submit A) Email verification is required and a code will be sent to user email B) Send email when others join the trip and the email should include the new trip cost (trip cost per person would go down when more join). Third action is hidden from the user , and will occur when group number reaches 3 , a trip confirmation email is sent to all participants with PayPal invoice for 50% of each person amount , the trip would be marked as confirmed and waiting for another 4 persons to join . General Notes: • The trip that the user creates will be listed once he activate his email address (one row list-table that includes number of days, where to go, number of participants -so far - , when to go , confirmation status and two buttons beside this row ( join , and change ). Join will allow others to select this trip and join it , change will allow the user who create the trip to remove him self of it or change the number of users with him , if he removes him-self and no others join then the trip will be deleted completely , but if others already join then he will be removed from the users count but the trip will not be deleted . • Trip number of Days is selective from 1 to 6 (Fixed) • The option to add trips to the number of days, ie. When the user choose number 1 he will have a drop down box to choose different destinations ( we will start with two – Petra & Dead Sea ) , but later on we will add new destinations to 1 day selection and to other days as well. • Each trip has two prices according to the number of participants. From 1-3 Price “Price A” , and From 4-7 Price. Price “B= (Price A/3) * 4 ” always , so when we enter the trip we would have the option to enter Price A , and the system will calculate price B