Codez une application Android

I want to replace my time sheets by an Android app. I want to send employes number, First name, last name, in a project to the foreman. (Thoses projects include different Activities). The foreman enter for each employe his hour (example: 9:00 to 22:00). It has to be compatible with a 7inch tablet. The output of the data has to be on a excel sheet in a specific form. The app has to keep the information in memory until the tablet has an internet connection to send it in a excel specific format (from the foreman to the main office). There is some basic validation to do. Example, an employee can't work more than 24 hours a day...can't do 2 activites at the same time, etc. Thank you for your time.