From what I can understand is that, you have an LCD code, an ADC code and a Heart Beat Monitoring code which you want to load it as a whole program in the microcontroller, right?
I'm not sure if this is what you wanted: Make a new project, and in that save the LCD and ADC code as LCD.h and ADC.h and make the Heart Beat Monitoring code as the main function. And include the custom header files as shown below.
Code:
#include<reg51.h>
#include"LCD.h" // for custom header files <> cannot be used instead we've to use ""
#include"ADC.h"
Now you can all any functions declared in the ADC or LCD in your main function.