How to measure elapsed time using MSP430
In Up or Up/Down mode, you would need a specific value for CCR0. The only mode that makes sense is Continuous.

To measure the length of an interval, read the current timer value (TAxR) both at the start and the end of the interval, then subtract them. This gives you the number of ticks, which you can convert into milliseconds if you know the number of ticks per seconds.

You run into problems when the interval is longer than 216 ticks. If that is possible, you can increase the length of a tick by dividing the clock source down.