diff --git a/google_sheet_handler.py b/google_sheet_handler.py
index a08c2b2f..881549d2 100644
--- a/google_sheet_handler.py
+++ b/google_sheet_handler.py
@@ -24,6 +24,22 @@ class GoogleSheetHandler:
         self._all_data_with_headers = []
         self._header_rows = 5
 
+    def _get_col_letter(self, col_idx_1_based):
+        """
+        Konvertiert einen 1-basierten Spaltenindex in den entsprechenden
+        Google Sheets Spaltenbuchstaben (A, B, ..., Z, AA, ...).
+        """
+        if not isinstance(col_idx_1_based, int) or col_idx_1_based < 1:
+            self.logger.error(f"Ungültiger Spaltenindex ({col_idx_1_based}) für _get_col_letter erhalten.")
+            return None
+
+        string = ""
+        n = col_idx_1_based
+        while n > 0:
+            n, remainder = divmod(n - 1, 26)
+            string = chr(65 + remainder) + string
+        return string
+
     @retry_on_failure
     def _connect(self):
         if self.client: return True