for Push.

IO/Excel/ExcelColumnHelperUxer.cs

@@ -0,0 +1,26 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace KssSmaPlaLib.IO.Excel
+{
+    public static class ExcelColumnHelperUxer
+    {
+        public static string GetExcelColumnLetter(int columnNumber)
+        {
+            if (columnNumber < 1)
+                throw new ArgumentOutOfRangeException(nameof(columnNumber), "Column number must be >= 1");
+
+            string columnLetter = string.Empty;
+            while (columnNumber > 0)
+            {
+                columnNumber--; // Adjust for 0-indexed calculation
+                columnLetter = (char)('A' + (columnNumber % 26)) + columnLetter;
+                columnNumber /= 26;
+            }
+            return columnLetter;
+        }
+    }
+}