setting a Calc document to default

I didn't get you clearly.But what I feel you are asking is that you want a .xls or .ods or .ots to automatically open with Spreadsheet.If thats what you want then right click on the file and go to properties.A dialog box appears.There choose open with tab and click on add button & add the spreadsheet application.Now make sure that it is selected and click on close.Now the file should automatically open with spread sheet.

If this is not what you want then please be a bit more clear.

 Should have been clearer; it is an .ods document that I wish to appear first after opening Open Office Calc and I wonder if an icon can be placed in the Ubuntu task bar; that I might simply click on that icon thus going directly to the spread sheet in question.

Have been successful, with your instruction, up to the point of locating the "open with tab"? My Open Office version is 2.4.1. Also, I may be overlooking something.

Thank you for a fast reply.

Bob,

Sorry that I couldn't reply you immediately as I was busy.

Yes you can place the an icon of the application on the task bar.Just click on the application and just drag and drop the application.You can also do it for a file but I am not that sure on how to do it for a file.
(NOTE: The task bar in ubuntu is placed on top not at the bottom.)

AFTER GOING TO OPEN WITH TAB:

Then you should see an ADD button.Click on it.Then another window would open there choose Open Office.org Spreadsheet.
(NOTE: It doesn't matter what version of open office you have.)