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;