Parameter and Command Reference > Connector Framework Server Parameters > Import Tasks and their Parameters > PreN 

PreN 
Identify a task to call before documents are imported and indexed into IDOL Server. Tasks must be numbered starting from zero (0). You can specify a Lua script or the IDX Writer. The IDX Writer is included in the Connector Framework server and generates an IDX file.
You must specify the task using the following format:
PreN=TaskType:Path_to_Script or MyTaskSection
where TaskType could be Lua to specify a Lua script, or IdxWriter to specify the CFS IDX Writer.
Parameters that should be passed to the task can be specified in a corresponding configuration section. This is optional. For example:
Post0=IdxWriter:IdxWriting
[IdxWriting]
IdxWriterFilename=Job0.idx
IdxWriterMaxSizeKBs=100
IdxWriterArchiveDirectory=./IDXArchive
In this example, the Pre0 task creates a backup IDX file (Job0.idx) in the IDXArchive directory using the IDX Writer.
 
Pre0=C:\Scripts\pretask1.lua