Getting a Column Number

[dhk <dhkuhl optonline net>]

The following will get me the Column from a treeview, but from 
focus_column I don't know if I'm in the first, second, third . . . or 
last column.

GtkTreePath *tp=NULL;
GtkTreeViewColumn *focus_column=NULL;
gtk_tree_view_get_cursor(GTK_TREE_VIEW(treeview), &tp, &focus_column);

How do you get the column number from a GtkTreeViewColumn pointer?  Is 
there a way to get the previous and/or next Column or column number?

Thanks,

Dave