protection of a workbook + unprotecting specific cells + calculation auto

hello,

I am new here (and pretty new to vba too!). I would have a couple of questions that I hope you can help me with.

in terms of performance is it better to turn off the automatic calculation in workbook_open and turn it on again when launching a macro?

I have just learned how to protect a workbook and its worksheets.
now users can no longer move/add/delete worksheets and change data within the worksheets.

now I'd like to allow users to change data in specific cells.
so: is it possible to unprotect cells in the workbook that are colored in grey? (and prevent users to change the color of the cell)

thank you
+++
alex

hi dave, thanks for your reply!

I have managed to find a code in vba to allow users to use cells of a certain color:

PHP Code: 

Sub UnprotectYellowCells()
     'Macro purpose:  To unlock all green cells
     'NOTE:  All worksheets in the workbook must be
     '       unprotected before this procedure is run
     
    Dim cl As Range, ws As Worksheet, lColor As Long
     
     'Set the cell color that you want to protect
    lColor = 36 'yellow
     
     'It may be a good idea to test all sheets to see if any are protected
     'here.  One method to do this would be to test the function found here
     'http://www.vbaexpress.com/kb/getarticle.php?kb_id=551
     
     'Cycle through each worksheet in the workbook
    For Each ws In ActiveWorkbook.Worksheets
        For Each cl In ws.UsedRange
             'Change colored cell to unlocked, and
             'all other cells to locked
            If cl.Interior.ColorIndex = lColor Then
                cl.Locked = False
            Else
                cl.Locked = True
            End If
        Next cl
    Next ws
     
End Sub 


works like a charm.