Maxscript: This demonstrates how to scale a set of verts based on a transform/center point.

Scale Verts | .ms

/* Scene Setup */
delete objects
ref = plane width:100 length:100 widthsegs:1 lengthsegs:1 wirecolor:yellow pos:[0,0,-1]
obj = convertToPoly (snapshot ref)
obj.pos = [0,0,0]

/* Scale Verts */
sca = [0.9, 0.9, 0.9]

-- array of vert positions
vertIds = polyOp.getVertsUsingFace obj 1
vertPosArr = for v in vertIds collect polyOp.getVert obj v

-- find center point for scale
center = [0,0,0]
for p in vertPosArr do center += p
center /= vertPosArr.count

-- scale
m = (transMatrix -center) * (scaleMatrix sca)
for v in vertIds do 
( 
	pos = (vertPosArr[v]*m) + center
	polyOp.setVert obj v pos
)
completeRedraw()