Try with your revisited code, maybe it's closer to your needs.
Code:
Option Explicit '<=added
Dim item_counter '<=added
Sub compare_dollars_Click()
Dim item_row, get_input, var1 '<=added
item_row = Worksheets("Sheet1").Range("C" & Rows.Count).End(xlUp).Row
For item_counter = 2 To item_row
get_input = Worksheets("Sheet1").Range("C" & item_counter).Value
If WorksheetFunction.CountIf(Range("C:C"), get_input) > 1 Then
var1 = Range("B" & item_counter)
MsgBox ("Sale Price" & " " & var1 & " at row " & item_counter)
End If
check_threshold (get_input)
Next item_counter
End Sub
Code:
Sub check_threshold(get_input)
Dim repeat_cell_address, newrow, var2 '<=added
Set repeat_cell_address = Worksheets("Sheet1").Range("C:C").Find(get_input, _
after:=Worksheets("Sheet1").Range("C" & item_counter), lookat:=xlPart) '<=changed
newrow = repeat_cell_address.Row
MsgBox (newrow)
var2 = Range("B" & newrow)
MsgBox ("Second occurrence of item code" & " " & var2 & " at row " & newrow)
End Sub
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