Hi armarni,
I'm sorry, since the time is not a part of the market's name as we received it from BetFair, and because the program adds the time tag, there is no way to look for 14:50 in the Market Locator.
What you can do instead is to load all markets and then delete the ones you don't need using a trigger. Now in triggers you can check the time tag in the market's name, so add this condition to the trigger:
Market's Name does not contain "14:50"