Regarding Running Batch Files And Different Packages

I have created a master controller package which runs as follows

deletes all the log files -> deletes few flat files on different drives -> preprocess task(execute package task) -> c# executable (execute process tasks) -> postprocess tasks (execute package tasks)

i need a create a task just before the preprocess task with an user input asking whether he wants to run a particular batch file before proceeding to preprocess. if the user says yes it should run a batch file followed by preprocess tasks, c# and post process or else it should directly goto preprocess, c# and post process (neglecting batch file task)

can anyone help me how to do it.