Runtime error 6 Overflow

Sub DB_Button_Click()
Load DB_UserForm....................hier kommt auch eine Fehlermeldung
DB_UserForm.Show
Unload DB_UserForm
End Sub

Sub DB_ListBox1_Change()
UpdateListBox Me.DB_ListBox2, Me.DB_ListBox1.ListIndex ' update the items in ListBox2
End Sub

Sub UpdateListBox(lb As MSForms.ListBox, IndexValue As Integer)
Const FirstInputRow As Integer = 5
Dim LastInputRow As Integer, ColumnIndex As Long, InputRange As Range
ColumnIndex = IndexValue + 2 ' determine which column to get list items from
LastInputRow = Cells(FirstInputRow, ColumnIndex).End(xlDown).Row ' determine the last input row
Set InputRange = ActiveSheet.Range(Cells(FirstInputRow, ColumnIndex), Cells(LastInputRow, ColumnIndex))
With lb
.ColumnHeads = True ' use the row above input range as header
.RowSource = InputRange.Address ' set the input range
'.RowSource = "'" & ActiveSheet.Name & "'!" & Range(Cells(FirstInputRow, ColumnIndex), Cells(LastInputRow, ColumnIndex)).Address
'.RowSource = Range(Cells(FirstInputRow, ColumnIndex), Cells(LastInputRow, ColumnIndex)).Address
.ListIndex = 0 ' select the first item
End With
Set InputRange = Nothing
End Sub

Sub UserForm_Initialize()
With Me
UpdateListBox .DB_ListBox1, -1
End With
End Sub