Move 2 parts of the mesh equidistance away from, or towards one another?

Hey guys,

Seems like quite a simple command, yet I cannot find any info on how to do it.

I see there are ways of using push/pull in object mode, but what about in edit mode? I dont want to separate the mesh into 2 objects? Nor do I wish to use a mirror. What am I missing? After pressing S (to scale) and X (on x axis) is there another button to prevent it from actually scaling the object, but still moving it along the axis?

Thanks in advance
Erratic

If this is symetrical then you can use symetrical axis X (top left the butterfly like symbol)…

Superstar! After all this time, I knew it had to be there somewhere! Thank you very much