The pronto has a clock with sufficient accuracy for what you want. You can read the clock and based upon its value alter the operation. It will require prontoscript however.

the actual Prontoscript code is quite simple. The information on the clock is not (as I recall) discussed in the pronto Developers guide, but since it is JAVAscript any good Java reference will discuss it.

I use a JAVA function to get the date time in seconds in a lot of my code as that is quite simple.

For example
LT=new Date();
localHours=LT.getHours(); // this is now the hours field of the date
localMinutes=LT.getMinutes(); // This is now the minutes field of the date