Chaining user-defined commands [duplicate]

Assuming I have defined 2 commands in .vimrc

MultipleEmptyLinesToOneRemoveExcessiveSpaces

I can run them in command-line mode:

:exec "'<,'>MultipleEmptyLinesToOne" | exec "'<,'>RemoveExcessiveSpaces"

However this method doesn't support auto-completion while typing the commands.

I know that I can create a new user-defined command that runs them in a sequence:

command! -range RemoveExcessiveSpaces2 exec "'<,'>MultipleEmptyLinesToOne" | exec "'<,'>RemoveExcessiveSpaces"

but it would be still great to know whether I can type (chain) any user-defined commands in command-line mode and have auto-completion at the same time.