Mitsubishi PLC Decimal to Hex

Hi
I'm using Mitsubishi FX5U with a GOT HMI. I need to enter values on HMI in decimal format then convert to HEX for use on a Modbus RTU link.
Anyone any ideas how this can be done as I can't find an instruction.

Modbus RTU transmits the pure binary value, if you have the value stored in a PLC register, you have to transmit the bytes just as they are.

Because Modbus RTU transmit the binary value it needs all the 8 bit in a byte and it will not work in a 7 bit serial communication.

The problem will be different if it uses Modbus ASCII then value must be converted to the HEX representation in ASCII characters prior to transmit.