"open with ..." lets the user choose from a list of applications (i.e. openwith does NOT know whether to start, say, Word or OpenOffice or whatever), so IMO it doesn't make much sense, to say "start with WORD *like* openwith". They are different concepts, so you should make up your mind what you want.

If you know that on the host your program is going to run, an association is set up between document files and the WORD application, you can just "run" the name of the word document:

system("yourdocument.doc");
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If you want always to use Word, no matter what association has been set up, you do something like

system("\\Your\\Path\\To\\Word\\winword.exe yourdocument.doc");
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