CTL on MSP430: One-shot timer?

Hello,

I would like to implement a retriggerable one-shot timer under CTL. It will be used to detect an idle line on a UART. Every time a character is received, I want to re-trigger the timer. If the time expires, it means that no character was received in that time. I interpret the expiration of the timer as an idle line, and terminate the message.

Is anyone aware of a good way to implement this? Thanks in advance for your help.