Moving 4 x BCD's into an Integer

Hi,

I'm communicating with a generator controller via Modbus, and not sure how best to write the time to it.

The generator is expecting the following:

MSB1 =BCD(hour)
LSB1 = BCD(minute)
MSB2 =BCD(second)
LSB2 = 0

If I convert the RTC values to BCD, how would I go about concatenating them and sending it as a single 16 bit Integer via a write MSG instruction?

Thanks