Rico,
If you want to enter the same value in the same cell in each sheet in the workbook, you can group the worksheets
- click the first worksheet tab
- Shift-click the last worksheet tab
all worksheets are now grouped.
Just about anything you do now in the visible worksheet will take place in all other grouped worksheets, such as entering data, changing formatting etc.
Don't forget to ungroup when you're done.
To group selected worksheets, Ctrl-click the sheet tabs.
HTH
Anders Silvén