Integer conversion from 8 bytes to 4 bytes

Anyone can suggest which function/operator in DeltaV can do the above conversion, please advise

I'm translating this from 3 party gas detector system software logic where it uses RND (round) & DBLINT (double to integer) before send the data to DeltaV DCS, thru MODBUS 

Floating point --> RND --> DBLINT ======== MODBUS======= DeltaV DCS -

Getting the correct value from the conversion, unfortunately not all the data sent in this format few of them sent in floating point format, i have to use same function to convert the data in the DeltaV. so i need to know the equivalent operator for RND & DBLINT to be used in DeltaV