Retrieves the width of a tile in dialog box units
(dimx_tile key)
The coordinates returned are the maximum allowed within the tile. Because coordinates are zero based, this function returns one less than the total X dimension (X-1). The dimx_tile and dimy_tile functions are provided for use with vector_image, fill_image, and slide_image, which require that you specify absolute tile coordinates.
(setq tile_width (dimx_tile "my_tile"))