Read the following article for your requirement:
Scheduling BODS Jobs Sequentially and Conditionally
As you have flat or excel files you can create file format or I am assuming here that you have already created it.
Now you can schedule your first job as when file comes so when first job will execute , after checking it's status whether it executed successfully or not , you can schedule another job as shown in article.
You can ask your source team who is sending you files , the timing by which you can expect the daily files & according to that schedule your job.
Check below links for further details:
different ways to schedule jobs in data services
Steps to schedule BODS job using BOE scheduler on the event of file creation
I hope this will help.
Thanks,
Swapnil