Comport usage?

I have a RS232 port I am talking to. I have data coming in that I am monitoring, but when I don't want to monitor the data, I want to send a command to the device to either send a differentr data or stop the data. Now when there isn't data I can send commands and I have no problem, but when the data is coming in, I am unable to send the commands. Does anyone know a way to send the data, maybe disable the comport to get data and be able to send the command?or at least know where I can get the info?

thanks

If you have a look at this webpage you should see how to set the RTS (Request To Send) and DTR (Data Terminal Ready) signals on your RS232 link. Note that you will have to make sure that these are wired in your RS232 cable - it won't work if you've only got Rx and Tx cabling with links in the connectors to hard-wire the RTS, DTR and DSR lines.

Hopefully the device you are communicating with will take note of the RTS and DTR signals and start/stop sending data accordingly.