Alex,

That is exactly what I was looking for, with a slight modification I was able to apply the validation to a range of 12 worksheets. A thousand thanks!

'Best method!!!

Dim N As Long
Dim WS As Worksheet


For N = 1 To ThisWorkbook.Worksheets.Count - 3 'added the -3 to exclude other worksheets
    Set WS = ThisWorkbook.Worksheets(N)

With Range("A10:A14,A16:A21,A23:A33,A35:A41,A50:A54,A56:A61,A63:A73").Validation 'Apply validation to this ranges of cells
        .Delete
        .Add Type:=xlValidateList, AlertStyle:=xlValidAlertStop, Operator:= _
        xlBetween, Formula1:="=Key!$C$2:$C$100" 'Retrieves the list from another worksheet named keys
        .IgnoreBlank = True
        .InCellDropdown = True
        .InputTitle = ""
        .ErrorTitle = ""
        .InputMessage = ""
        .ErrorMessage = ""
        .ShowInput = True
        .ShowError = True
        
    End With

I did figure out an alternate with .select, however it would flip through all the worksheets when ever I opened excel. I am posting this because the.select method is all over the internet and I DO NOT!! recommend using the method below.    

Dim N As Long
For N = 1 To ThisWorkbook.Worksheets.Count - 3
    ThisWorkbook.Worksheets(N).Select

Range("A10:A14,A16:A21,A23:A33,A35:A41,A50:A54,A56:A61,A63:A73").Select
   With Selection.Validation
        .Delete
        .Add Type:=xlValidateList, AlertStyle:=xlValidAlertStop, Operator:= _
        xlBetween, Formula1:="=Key!$C$2:$C$100"
        .IgnoreBlank = True
        .InCellDropdown = True
        .InputTitle = ""
        .ErrorTitle = ""
        .InputMessage = ""
        .ErrorMessage = ""
        .ShowInput = True
        .ShowError = True
        
    End With