How to debug a word add-in class library loaded in an external application?

Question

I developed a word add-in (a dll), which can be debugged in word. (in this case, when I press the debug button, word starts up)

but there is another application called wps that can also load word add-ins. this application is located at D:\Program Files\Kingsoft\WPS Office\11.1.0.11744\office6\wps.exe, so I set Start external program to this directory.

But if I start debugging, the breakpoints are ignored by visual studio. What do I need to do now?