var doc = context.document;
var page = doc.currentPage();
var current_artboard = page.currentArtboard();
var grid_width = [[doc askForUserInput:"How wide do you want your grid to be?" initialValue:"960"] integerValue]
var column_count = [[doc askForUserInput:"How many columns do you want?" initialValue:"12"] integerValue]
var gutter_width = [[doc askForUserInput:"How wide do you want your gutters to be?" initialValue:"20"] integerValue]

if (grid_width != 0 && column_count != 0 && current_artboard != null) {
	var horizontal_rulers = [current_artboard horizontalRulerData]
	var gutter_count = column_count + 1;
	var space_for_columns = grid_width - (gutter_count * gutter_width)
	var column_width = space_for_columns / column_count
	var frame_center = [[current_artboard frame] width] / 2
	var start_grid_at = frame_center - (grid_width / 2)

	var ruler_count = (column_count * 2) + 2
	for (var i=0; i < [ruler_count]; i++){
	  [horizontal_rulers addGuideWithValue:start_grid_at]
	  if ((i % 2) == 0) {
	  	start_grid_at += gutter_width
	  } else {
	  	start_grid_at += column_width
	  }
	}
}