How to get data from serial port and process it?

Hi every one, I am doing AUTOMATIC IRRIGATION AND DISEASE CONTROL SYSTEM which will take 3 sensor readings as input and based on that values it will monitor the watering..(on/off). And for disease controlling every time it will compare the sensor readings with the disease condition values(different for different crops), whenever condition satisfied it will on the buzzer or intimate the farmer via sms.

Up to this i can..the problem is that i want to create a matlab gui for this project which will display all readings which are comes from serial port and also i want to display real time and date in my GUI. If disease condition reached corresponding message should be displayed in message box. please find the attachment.. The layout is simple ....i have basics with all options in GUI...but i need to know that getting serial data and processing it according my project.... please help me with this.. Thank you