This will work regardless of which sheet you're on as long as the workbook you want it to work in is the active workbook:
Code:
Sub ProtectFormulaCellsInTable_tAbstract()
With Range("tAbstract")
.Parent.Unprotect
.SpecialCells(xlCellTypeFormulas).Locked = True
.Parent.Protect
End With
End Sub
Changing the message when someone tries to change a locked cell on a protected sheet is not possible (afaik) but something else can be done, see:
custom error message in popup window for protected cell? | MrExcel Message Board
…but is it worth it?