Conditional loading the files

HI All,

I have two files data of two departments.

if file exist then only need to run the data flows.

IF one file exist it should run only one.

PLease provide the steps.

THanks in advance.

DAta is like this:

DEpt10 data:

EMpno,Dept,SAL

1,10,100

2,10,200

3,10,300

DEpt20 data:

EMpno,Dept,SAL

1,20,1000

2,20,2000

3,20,3000