Detecting High to Low trans

I'm currently using the rx and tx on com1 to control a device and was planing to use RTS & CTS to send then receive a voltage to and from a relay BUT
I want to make sure the relay whent from low to high or high to low and then back high depending on the start state.

does anyone have code to detect a transition like this?

I'm extreamely frustrated its been almost a full day of doing nothing but this. its becoming more emasculating then an E.D Problem...

thanks :confused:

if you are not using another pin, DCD for example, you could use it to montor the sate of the relay.