Is it possible to create a wordpress dashboard plugin that will span all the columns that the user has chosen to display? I know how to force the user to only display one column but I would rather leave them that freedom and span the number of columns that they have selected. Be it one, two, three or four. Thanks.
No you can't - a metabox cannot span more than one column, and so the width of the metabox is determined by how many columns there are.