Hi, Vinicius -
If I may ask, what are you wanting to accomplish? There may be existing functionality in PowerBuilder that does what you need. Please also mention the version, release and build of PB that you are using. It would be helpful to also know the version of Windows being used and if your application will be deployed as a 32-bit or as a 64-bit application.
As to your question, the argument value to this Windows API function is a structure. Here are links to API documentation:
https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-trackmouseevent
https://learn.microsoft.com/en-us/windows/win32/api/winuser/ns-winuser-trackmouseevent
The first URL is for the TrackMouseEvent event, and the second URL is for the structure.
Please recognize that the Windows API documentation is written for C/C++ development and the API makes extensive use of typedef'd data types, so you'll need to translate everything into PowerBuilder/PowerScript equivalents.
Best regards, John