Hi Wade,
one way you could go is with field calculator:
1. create fields for centroidX/centroidY of the grids, calculate geometry for them.
2. create fields for UpperY, LowerY, LeftX, RightX
in field calculator you can then calculate each field:
UpperY = centroidY + (gridheight*0.5)
LowerY = centroidY - (gridheight*0.5)
LeftX = centroidX - (gridwidth*0.5)
RightX = centroidX + (gridwidth*0.5)