Google script coding (Boulder)

Hello, I need someone to do some coding in google script to create calendar events and automatically make invoices for my landscape company.
I need sheets and calendar to communicate with each other and pull data from sheets (pulling people's names, cost of services.
.
.
) to make events that my crew then can add in the hours worked and say they have completed.
It will then make an invoice from it.
The invoice will be for the whole month and 3/4 through the month should have an option to have us double check it and approve.
Once approved it uses the same database that it pulls all the other info from sends the email to the correct email.
If you are interested in doing this please let me know how long it will take and your assumed cost.
Thank you!