Need macro which locks cells (C57:C61) based on data validation selection (C1)

Welcome to the forum! Do you want the cells to lock instantly once the selction is made, or do you want the user to make the selction, then click a button to apply the change? It would also be helpful if you'd consider posting a sample workbook.

On your keyboard, press Alt + F11 to open the code window.
Double click ThisWorkbook, and paste in this code:

Private Sub Workbook_SheetChange(ByVal Sh As Object, ByVal Target As Range)
ActiveSheet.Protect DrawingObjects:=False, Contents:=False, Scenarios:=False
    If Range("HireType").Value = "Pre-Hire Re-Hire C to I Conversion" Or Range("HireType").Value = "Pre-Hire - C to I Conversion" Then
        Range("C1:C57").Locked = True
        ActiveSheet.Protect DrawingObjects:=True, Contents:=True, Scenarios:=True
        MsgBox "No Referrals for C to I conversions", vbExclamation, "Warning"
    Else
        Range("C1:C57").Locked = False
        ActiveSheet.Protect DrawingObjects:=False, Contents:=False, Scenarios:=False
    End If

End Sub

Note that you need to name your data validation drop down HireType for this code to work.