Hi Chris,
This function was put in place for the older AT boards. For modern, PCI or PXI versions of the DIO-32HS, 6533, and 6534, this function is ignored. The Traditional DAQ C Function Reference help file contains a note that says the function is for AT products only. In which manual were you looking? I can help make sure the available documentation adequately represents the status of this function.
I hope that helps.
Allen