You can use a lua script to operate the mouse, but I would not recommend this. You would need to move the mouse cursor to the correct position before sending the click, and the position could change depending on the view. Note that the versions of FSUIPC for P3D and FSX had a mouse macro facility, for sending mouse clicks to specific 'mouse rectangles' defined in the aircraft. However, this facility is not available in FSUPC7 as MSFS does not support this.
There are 3 different ways that you can achieve this:
1. Define your own preset to activate all of them (in the myevents.txt file) and use that. Just define the preset to send the calc code of each individual preset. I showed how to do this for the PMDG 777-300ER in another post:
Not sure if they work in the 777-200. You can try them - or correct to use the 777-200 light presets if different.
2. Define a macro to send each light preset. Macros can be used to send multiple commands on a single button or key press - see the Advanced User guide for details un using macros.
3. Overload your assignments so that you have multiple preset assignments on the same button. To do this, assign the first preset. Then open the FSUIPC7.ini file and comment out the assignment (add a semi-colon after the '=' sign) and reload the assignments. Then assign the next preset. Then comment that one out. Repeat until you have all the assignments you require, then uncomment out the assignments previously commented out.
When doing this, make sure that you edit the FSUIPC7.ini file with the button assignments panel open, and click 'Reload all buttons' when you have saved the changes, to reload the file.
John