Grahammal,

In this situation I always start by protecting the all cells in the
whole worksheet and un-protecting the few that I want users to be able
to enter data into.
this can be done via the 'Format' > 'Cells' menu items but I always
find it easier to put the Lock Cell tool onto the toolbar....

View > Toolbars > Customize > Commands Tab > Format and drag and drop
the 'Lock Cell' tool to a visible toolbar.

Now you've got this tool showing, highlight the whole worksheet - Ctrl
+ A and click on the padlock tool, then select the cells you want free
to enter and click on the padlock to set them as unlocked.

The formats you just added will only restrict changes when you protect
the worksheet by selecting 'Tools' > 'Protection...' > 'Protect
Worksheet'.

One word of warning, if you lock a cell which is changed by clicking on
a radio button or other element in the forms toolbar, it will tell you
the cell you are editing is protected. Unlock these cells before you
protect the worksheet.

Hope this helps.