Check this OLD article I wrote.

In Flash 5 you could have spaces in your argument to EXEC so you could do a LOT more than you could with Flash MX and later versions.

The only reason to use the proxy tool with Flash 5 would be to get rid of the ugly DOS box. With Flash 5 you can pass arguments to the proxy.exe and it will pass them along to the BAT file so you can use one copy of PROXY and one BAT file to do all your work. If you don't care about seeing the DOS box appear then you can just follow the example in the article.

Read the rest of the stuff at too, there's a lot of stuff there that will help you with Flash 5 sutff.