Excel found unreadable content - Data Validation

Question

I have some combo boxes that I populate on opening of the workbook - the source of the data comes from a database.

I populate my combo boxes using data validation wi

Answer 1

It seems that you are right with the string length of Validation formula1 parameter. My suggestion for you is as follows (additional information are placed as comments within the code):

'Split your list into array, or if data are Array before you _
create List variable you could combine some of earlier steps _
of your code

    List = Split(List, ",")
'paste your list into hidden sheet as of A1 direction bottom, _
we need to transpose our Array to do so
    Sheets("hidden").Range("a1").Resize(UBound(List) + 1, 1) = Application.Transpose(List)

 With Selection.Validation
    .Delete
    'here we need to change definition of formula
    .Add Type:=xlValidateList, AlertStyle:=xlValidAlertStop, Operator:=xlBetween, _
    Formula1:="=Hidden!A1:A" & UBound(List) + 1
    .IgnoreBlank = False
    .InCellDropdown = True
    .ShowInput = True
    .ShowError = True
  End With