BAPI_HU_DELETE

Hi,

I am getting a error in all of the Bapi's related to HU.I am trying bapi_hu_empty and all the bapis which could be used to empty or delete the Hu numbers...

The follwoing error is coming :

Processing of HUs for selected objects not possible

Please suggest what is the error.........

or pls suggest any method to empty or delete the handling unit numbers in delivery

Kanishak