Assign a part of a register for later use?

If I have a register like

signal REG : signed (31 downto 0);

and I will use every part of it for other purposes, it'll be a mess if I just take the whole part like

REG (31 downto 24) <= ...

REG (23) <= ...

REG (22) <= ...

Do you know if we can assign it to another description without adding signals? like

Data <= ...

Flag <= ...

ACK <= ...

The software will understand Data will be REG (31 downto 24), instead of make another signal and let REG (31 downto 24) <= Data;