Defining custom screen commands?

[Dun Peal]

Folks,

There's a sequence of screen operations that I execute every once in a
while. I can use `bind` and `eval` to execute it by keystroke, but it
is not used commonly enough to justify a keystroke binding.

Is there a way to define it such that I can execute it by running a
custom command on the `C-a :` command line?

So for example, I'd define it as custom command `foo`, such that when
I hit `C-a :` then type `foo` and press enter, the sequence of screen
commands gets executed.

Thanks, D.