protecting worksheets from deletion

Is there a way to protect worksheet/workbooks from being deleted after the user is in the spreadsheet?

Tools\Protect\Protect Workbook.
You may also set a password, and your users will not be able to delete the sheets. Is that you need?

You can protect a worksheet or an entire workbook, see here: http://www.rmgsoftware.com/xl/xl048.htm
so others can not make changes, unless they know the password. To make changes you would need to first unprotect the worksheet. It is possible to protect a worksheet, yet leave individual cells unprotected, so users can input data to those unprotected cells, but not alter the protected area of the worksheet.