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There is a way, and that is to display the message using a batch file. For your question above, the code will be as follows:

Code:

@echo off
echo Stand up, stretch, move, walk around
pause

Save this simple file as a batch file with the extension .bat. Give it a suitable name. The pause command holds the display, so that you have to click on it to dismiss it.

Now, follow the instructions in the link you provided and, instead of selecting the option to Display a message, choose Start a program. In the screen that follows (see below for an example) browse to the location of the batch file you created and then click OK.

I've had another look at this, and the solution is deceptively simple. It doesn't involve a batch file, rather you need to use vbScript.

Code:

MsgBox "Stand up, stretch, move, walk around.", vbSystemModal

Save this simple file as a vbscript file with the extension .vbs. Give it a suitable name. Again follow the instructions in the link you provided and, instead of selecting the option to Display a message, choose Start a program. In the screen that follows (see my post above) browse to the location of the vbscript file you created and then click OK.

You're welcome. :)