Need help understanding a RS232 to RS485 concept.

[Flyfish30]

For my project I will need to communicate at a distance of up to 200ft.  At the start point, I will be converting an RS232 signal to RS485 and at the end I will be using another RS485 chip to communicate with a microcontroller.  However, I am noticing some circuits differ with using the RTS (Request to send) line of the DB9.  This link shows the DB9's line being used

http://aquaticus.info/rs485_to_rs232#attachments

And this link shows the RTS line not being applied.  Furthermore, both RE and DE pins of the RS485 chip(s) are tied to ground both from the PC to the microcontroller:



Question is:  Do I absolutely have to utilize the RTS line?  Is it crucial?  I will be using a VB program to both send data to the microcontroller and receive data, such as temp, depth and heading.  Any help would be appreciated.  ???