{
	var proj = app.project;
	
	if (proj) {
		
		app.beginUndoGroup("Set Field Separation");
		// loop through all items selected in project window
		
		for (var a = 0; a < proj.selection.length; ++a) {
		
			thisItem = proj.selection[a];
		
			// check item is footage and is not a still image
		
			if (thisItem instanceof FootageItem && !thisItem.mainSource.isStill) {
		
				// set footage's field separation type.
		
				thisItem.mainSource.guessPulldown(PulldownMethod.PULLDOWN_3_2 );
	
			}
		}
		
		app.endUndoGroup();
	}
}