I need to modify a current bit of code

Sub newvers()
Range("A595:C595").Copy Sheets("PRODUCT INFO").Range("A" & Rows.Count).End(xlUp).Offset(1)
Range("A595:C595").Select
Selection.ClearContents
Range("A594").Select
End Sub

I need to make sure that the content of cell A595 is not anywhere in the sheet product info,
If it does exist within product info i would like a message box to be displayed and the code to stop running

any bit of help on this is much appreciated