C++ threads

[Striker]

I have a piece of C++ code that I am using to execute an external program via ShellExecute on a list of files contained in a ListBox object. The external program opens another window and begins execution, however, before the external program is completed, the parent process goes to the next file in the ListBox and begins the external program again. This is Ok if I only need to run it on a few files, but when I have 100 or more files in the list, I end up with 100 or more individual instances of the external program running at once, which of course brings my system to a screeching halt. I need to know if there is a way to pause execution of the parent process until the child process is completed. The external program reads a file and outputs another file based on the input file data, and I cannot modify the source code of the external program.

Any help would be greatly appreciated.