@Vipin,
May be you should have a step before each import task that checks for the existence of the file. This will enable you to conditionally skip the task/step if the file does not exist.
Another option is to use a for each file loop which runs over the files and process each file. However, you need to then do some conditional code based on the file you find each iteration of the loop.
commented on Jul 18 2012 7:07AM