🚀 go-pugleaf

I have made a help file for my application in .pdf format. I use the 
following command to open it on help button click:

ShellExecute(0, "open", "help//help.pdf", NULL, NULL, SW_SHOWNORMAL)


How do I know if that file has been opened, I tried with following:

if (!ShellExecute(0, "open", "help//help.pdf", NULL, NULL, SW_SHOWNORMAL))
   Application->MessageBox("You need Acrobat Reader for viewing 
help","Information");

but it doesn't work, also I've tried

try
{
ShellExecute(0, "open", "help//pomoc.pde", NULL, NULL, SW_SHOWNORMAL))
}
catch(...)
{
Application->MessageBox("You need Acrobat Reader for viewing 
help","Information");
}

it also doesn't work. I just want to know if end user opened the file, 
and if he didn't I want to give him message to inform him that help is 
in Acrobat Reader format and he needs to install it in order to read help.