Dialog function errors

[ReignBough]

Is there a way to get the error a dialog function encounters? Example, DGAppendDialogItem() returns 0 if an error was encountered. But what is this error? Did I pass a wrong ID, type, sub-type, etc? Is there a function that I can call to get this error, like GetLastError().

EDIT 1: 2014 Sep 10

I asked this since I am unable to add a button on AC18. Here is my code:

short my_idx = DGAppendDialogItem(iDialId, DG_ITM_BUTTON, DG_BT_TEXT, 0, 10, 10, 80, 30);
if (my_idx == 0) WriteReport("[DialogTypes] Error! Cannot append ItemType: DG_ITM_BUTTON");
DGShowItem(iDialId, my_idx);
DGSetItemText(iDialId, my_idx, "Okay");

[ReignBough]

On EDIT 1

Found out that DG_BT_ICONTEXT is now used as sub-type for buttons.