Sure, it is a matter of writing the program for T100MD+. You can use a clock pulse to drive an up-counter and the value of the counter is displayed on the LCD as the time progresses. You can use one or more input to start, pause, stop and reset the counter.
Using 0.1s clock pulse will give you fairly accurately timing with a resolution of 0.1s. Although the T100MD+ PLC also supports clock pulse of 0.01s period, but you have to be careful that the program scan time is to be kept short so that the total program scan time is shorter than 0.01s in order to maintain the timing accuracy.
Alternatively, you can use a High Speed timer with 0.01s resolution and have it time down but when displaying the stop watch on the LCD you can show it as a positively increasing value by subtracting it from the timer set value. High speed timer will give a more accurate time base.
