The ExecFile macro is an alternative way of opening programs and files, and it's a little easier to program, but it has one major drawback: the ExecFile macro allows multiple application windows to open at the same time. Using ExecFile may inadvertently cause some users to open several copies of the same file or program. This can occur if a user double-clicks the ExecFile macro link, or an impatient user, while waiting for the program to open, clicks or double clicks again – thus opening another instance(s) of the program.
According to the Help Workshop, when you click a link using the ShortCut macro, "WinHelp runs the specified program if it is not already running. If the specified program is running, WinHelp activates it." In other words, WinHelp checks whether the window is running before executing the command, thus ensuring that only one copy of the program is running at a time. If the window is open, then it executes the command inside the already running window.
In addition, the Help Workshop states:
"If the wParam parameter is specified, a WM_COMMAND message with the specified wParam and lParam values are sent to the program." This is explained in the How To exercise that follows.
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