I just checked with an Edirol (by Roland) PCR-300. Unfortunately, it seems that "DT" can only be included in one copy of the SysEx and Free Message definitions, so the messages "B0 40 DT" and "B1 40 DT" can be programmed to it, but "B0 40 DT B1 40 DT" message is not possible.
Since the Edirol PCR-300 / PCR-500 / PCR-800 series are the predecessors of the Roland A-300PRO / A-500PRO / A-800PRO series, the A-500PRO probably works the same way.