hide and lock cells with formula using vba

Okay that means there are no formulae in that particular worksheet.

Try this code

Option Explicit

Sub LockFormulae()
    Dim rngHasFormula As Range
    Dim ws As Worksheet

    On Error Resume Next
    For Each ws In ActiveWorkbook.Worksheets
        ws.Unprotect
        Set rngHasFormula = ws.UsedRange.SpecialCells(xlCellTypeFormulas)
        If Err.Number <> 0 Then
            Err.Clear
        Else
            With rngHasFormula
                .Locked = True
                .FormulaHidden = True
            End With
        End If
        ws.Protect
    Next
    On Error GoTo 0
End Sub