This property is the network path to the input spectra of the spectrum specified by the index parameter. The filenames of the input files are composed from the batch_input_path, the batch_spectrum_filename and the extension defined in the 'Input options' worksheet of the batch control workbook.
You can read or write the batch_input_path.
VBA example:
wcd.batch_input_path(1) = "C:\test\data\trans\"
wcd.batch_input_path(2) = "C:\test\data\refl\"