CICS QUERY..NEED THE ANSWER BADLY

Hi Everyone ,
This question is bothering me for a while .
In CICS suppose there is a screen it is actually a BMS program
isn't it..?when ever we enter some data in the fields and hit
an enter the back end cobol program is invoked .In the cobol program
the BMS is identified through symbolic map .Now my question is how does
the BMS program or CICS knows which COBOL program to invoke..?Some
people said it is due to the presence of the corresponding symbolic
maps in the corresponding COBOL programs .Now If the symbolic map of
the same BMS map is present in 3-4 COBOL program which COBOL program does the CICS call when the screen of that BMS map is used
Thanks