set up a live agenda in a worksheet

I am trying to create an agenda that I can update as timing is adjusted throughout the day.  For example:

if a topic is due to be spoken of at 14:30 for 20 minutes, but it goes over by 5 minutes, I need to update the new start time and adjust the duration of the next topic that was supposed to happen at 14:50 for 30 minutes.  It will now happen at 14:55 for 30 minutes and therefore affect the rest of the pre-set daily agenda.  

Its similar to adding a day to a cell and then copying that formula to subsequent cells.  When I change the initial date, all other are adjusted as a consequence.  

I am finding this more challenging than I expected, but there must be a simple answer.