How implement "Identify Screen" function by NVAPI interface in window7/10 ?

Now i’m writing a tool to implement group mosaic function, like NVIDIA Control Panel, but have a problem here: how identify screen. Because the Monitors’ arrange order are not fixed, so need implement the function: when click a button, then the monitors will show the big “1”/“2”/“3”/“4” text on Screen. IS there some api can do this ?