you should in your properties window for the string that shows the text for time limit, Uncheck display as background, then using a Always condition and the set Change alterable string to work like this...
"You have "+Str$( >Enter countdown variable here< )+" Seconds to find the exit, Hurry"
You would end up using the expression editor to achieve this, The line you would enter into the expression editor would look pretty much like it does above, except the >Enter countdown variable here< portion you would pull the value of the countdown into it and it will convert it to a displayable string in line with the rest of the text.
Then, maybe a sound for each second it counts down, When playing I had no idea I had to run to the exit to meet a time frame.
GREAT JOB WITH YOUR FIRST TGF2NG Game!