Splitting map grids into smaller grids

[Anonymous User]

I have created a mapgrid for producing a mapbook and all is well.  My problem now is that I want to create another map grid that splits those grids into 4 parts each to create a smaller grid that exactly matches the larger grid (like quarter sections in the PLSS grid).  Sorry for the runon sentence.

I ArcGIS 9.3.1 with dsmapbook only.  Any ideas would be great.

Thanks

[MarkEllis]

Use the Create Fishnet tool to make a new grid.  Define the same origin point as your existing grid, but with X and Y offsets at half the existing grid value.