Gcode help

I am beginning to think that the Gcode interpreter in replicatorG is not a full implementation.

On my CNC machine if I want to do something periodically like blow swarf off the bed I can add loops and conditional branches. I can't work out any way to do this on the 3d printer.

If, for example, I wanted to wipe the head every 5 layers it should be something like this:

In start.gcode
#101 = 5 ;

In layer_change.gcode
WHILE [#101 GE 0] DO1
#101 = #101-1
END1

IF [#101 EQ 0]
#101 = 5
"WIPE HEAD gcode"

The problem is that no matter what I do it with, IF DO WHILE END all give errors as does declaring a variable with the #"variable" statement.

Are there any loop, decision making methods implemented?

Is it possible to read values back into your gcode. For example if I wanted to reduce my bed temperature by 5 degrees per layer is there a way to get current temperature and subtract 5 from it then use that to set the temperature?

It seems to me that this should be possible if the software is complete and for it to be really usable.