Loading application data when data file is double clicked in Windows Explorer

Hello!

In Delphi 7, how does one get an application associated with a given file
type to load data from a data file when it is double clicked in Windows
Explorer? I wish to be able to do this without registry settings. Imagining
that the double click might be translated into a shell command combining the
associated application and data file names, I tried to use ParamStr function
to extract the data file name from a shell command, but without success. Is
there an event handler or an API function for extracting a data filename
defined when the program is launched?

Thanks for any help.

Enquiring Mind