Hi SJG,
I spent some time trying to get this to work with a spreadsheet, but I never was able to. Maybe someone else can help you there. I can help with connecting to a simple database like access. It would probably be better for you to use a database as opposed to a spreadsheet anyway. Also, it looks like you're using Civil 3D; my instructions are in Map 3D, but they should still work for you.
1. Connect to the database. In your task pane, go to the "map explorer" tab, right click on "data sources", and click on "attach." This will open a standard windows dialogue box. Just select the correct file type (at the bottom), navigate to your data, select it, and click on attach. Once you do that, the database and any tables and queries should show up in the tree (see the "datasource" attachment).
2. Create a link template. The link template is what tells cad how to connect the data in the database to the data in the drawing. In the map explorer tab of the task pane, right click on "link templates" and select "define link template." This will open a new window. Select the correct database, the correct table, then give the link template a name (third line down). Finally, select the field that has the unique value that will be used to generate the links and click on "ok." The new link template should appear in the map explorer.
3. Link drawing objects to the database. In your drawing, the objects that you are attaching need to have object data with a unique identifier that matches the unique identifier in the database (see help on creating object data). Assuming that you have this allready, at the command line enter "mapod2ase" and hit enter. The dialogue box that pops up now has a few steps. At the top, you will need to select the object data table for your drawing objects. In the "target link template" section, select "link object data to database" and click on "define." In the define box that pops up, select the link template that you created earlier. Below this you will see two collumns, one called LT Key and one called OD Column. The LT Key is the key field that you set in the link template. The OD Column needs to be the matching key in the object data table (pick the correct field through the pulldown). Once you have selected the key, click on okay to go back to the first dialogue. Now you just need to select the objects that you want to link (can be done automatically or manually). Once you do that, hit "proceed." The linked data should now show up in the object properties.
Spreadsheets as in Excell are are no on, Tables in a database is the way to go. Also try to stay away from MS Office and Acess if possible. Data links is still there from the old school map but the new method is with FDO and data connect. There are free database (spatial database) that will work better in the long run.
Try experinebcing with SDF first and get the hang of how FDO works then either convert over to SQL express (free) or even MySQL if it's still available in the version that works in MAP3D.
Read anything you can on SQL and transactions, that;s the key to getting MAP3D to do this when you do that or in simple terms updates everything for you when "A" changes to "B".