This sounds like a learning exercise, so I will not provide you with some code. I will give you some ideas and see what you can do. If you have not looked at the online tutorials, they might be helpful.
For the button press: The program must still be in a loop. The program needs to continue running, you just want it to do nothing while waiting for the button. Hints: 1)a) Study the use of the event structure. 1)b) Poll the button with a case structure. 1)c) Shift registers are your friend.
For the Timed mode: How will the user provide the timing information? As a control? If the interval is specified in seconds, how will you change that into into the units required by the delay functions? Hint: In addition to the simple Wait (ms) function you are now using, there are some more advanced timing functions available (although you can do it quite easily with the Wait (ms)).
For extra credit add a switch to select the timed or button press modes and do both in one program.
Lynn
