Excel VBA Macro to create a drop down list

I have an excel macro that creates a validation drop down list. It does basically what I want but I would really like it to get the drop down list values from cells in another workbook. Right now it get the list from within the Macro therefore it is a fixed list that you have to edit the macro to change. Here is what it looks like now.

With Selection.Validation
        .Delete
        .Add Type:=xlValidateList, AlertStyle:=xlValidAlertStop, Operator:= _
        xlBetween, Formula1:="ALARM,AMER,CANTEEN,CHALK,CINTAS,CTYWTR,HILLYARD,HUNTER,SAFETYK,SAGUENV,SAGVENT,TEP,TUCSAFETY,WESTLAKE"
        
        .IgnoreBlank = True
        .InCellDropdown = True
        .InputTitle = ""
        .ErrorTitle = ""
        .InputMessage = ""
        .ErrorMessage = ""
        .ShowInput = True
        .ShowError = True
    End With

I want to be able to get a list from a file called Vendor.xls, in sheet 1 from cells A1:A30.

Or even if it could be pulled from a list in a different worksheet within the active workbook.

Any help would be greatly appreciated.