Adding grid cells to a grid index feature

Question

I've created a grid index for data driven pages. It consists of 2 rows and 6 columns. Now I would like to add additional rows and columns to the existing grid index while maintaining the position of the original 12 cells. the additional cells would be above and below the original grid.  How do I go about doing so?

FORESTWEBB · Answer

That works...simply wish there were a less tedious process.

SarahHartholt · Answer

easiest approach might be to to copy and paste one of the grid cell polygons, then snap to the vertices of your existing cells.