Switches in configuration files?

[Rt Ibmer]

Is there a way to create a variable in the config file that I can set to true or false (or 1 or 2, etc) and then make my location blocks do an IF operation based on that var to take different actions in the block.

For instance this is what I currently have:

 location ~* /maindir/area1 {
        error_page   500 502 503 504  /service-is-down.html;

        access_log  /main.log main;
        proxy_pass  http://my_farm;

        # To temporarily take service offline, comment out the 2 lines above, and remove the comments from below.
        # The incoming requests will then be logged for manual later handling.
        # access_log  /deferred.log main;
        # empty_gif;
        # expires -1d;
    }

And instead I'd rather have something like this:

 location ~* /maindir/area1 {
        error_page   500 502 503 504  /service-is-down.html;

     if(inMaintenanceMode == true) {
        access_log  /main.log main;
        proxy_pass  http://my_farm;
     }
     else
     {
        access_log  /deferred.log main;
        empty_gif;
        expires -1d;
     }
    }

Can this sort of thing be done and if so can someone please demonstrate with a tiny snippet? Thanks!