Instructions provided describe how to clip a grid based on another grid using Spatial Analyst.
- Select Properties from the Analysis menu.
- Set the Analysis Mask to the grid defining the area of interest and click OK.
- Select Map Calculator from the Analysis menu.
- Double-click the grid to be clipped from the Layers list box.
- Click Evaluate.
A new grid theme is created. To save the theme permanantly, make the theme active and select Save Data Set from the Theme menu.
The ArcScripts Web page has an avenue script that clips a grid based on a shapefile or coverage. Click the link below and do a keyword search for "clip grid".