I don't protect data much so I'm not sure what other solutions there may be.
But I think you could do this by writing a VBA program; it would use the
Worksheet_Change event, and set protection for the new cell if its value is
non-blank. That would save the protection between sessions, too. Dunno
whether you like that idea, though, since you posted this in the Worksheet
Functions group.

--- "enna49" wrote:
Is there anyway I can protect only cells that have data. eg after
entering data for a number of lines I would like to protect only the cells
that have data in one step.

Therefore when the worksheet is opened again the user can continue to enter
data and in one step protect what has been done.