This method retrieves the caption associated with a particular command item.
HRESULT GetCaption( long lIndex, long lItemId, long lItemData, BSTR *pbstrCaption );
NOERROR indicates success. E_OUTOFMEMORY indicates that the system is out of memory.
The IASProvidePowerListBoxCommandData::GetCaption method is called by the power list box control to obtain the display text for items with Null captions. It must be registered by calling IASPowerListBox::put_ProvideCommandDataSink. This method should return a SysAllocString BSTR because the power list box calls SysFreeString on it when drawing is complete.