This function can be used to add a given value (real or string) to all the values of the cells found within the defined area of a grid. The value to be added must be of the same type as that held within the grid cells, ie: you cannot add a string to a real or vice-versa, and for strings this corresponds to concatenation.
ds_grid_add_region(index, x1, y1, x2, y2, val);
|index||The index of the grid.|
|x1||The x position of the left of the region in the grid.|
|y1||The y position of the top of the region in the grid.|
|x2||The x position of the right of the region in the grid.|
|y2||The y position of the bottom of the region in the grid.|
|val||The value to add to the region cells.|
ds_grid_add_region(grid, 2, 4, 5, 5, ".")
This would add "." to all the strings held in the cells within the defined region of the ds_grid referenced by the variable "grid".