Fully Block/Nullify mouse movement/click

Question

Hi, I'm writing an application to run in background to fully control multiple mouse click/movement. (Raw input) For example, If I click a button, nothing should happens unless i tell it to (i.e. it won't give focus to some other application when i click the left button without my permission, even if I'm outside of my application boundary or when at the invisible/transparent part of the application, or my application is running in background). I'm currently clueless where I should start, please give me some direction. Thanks.