Excel Macro - Find and replace across two sheets

Hi all, I need an Excel macro to find and replace across two sheets. The below are the specifications. The macro is stored in an Excel file (triggered by a button). The sole purpose of this Excel file is for running the macro. It does not store any data. When the button is pressed, the macro would open, in the same folder, an Excel file that contains a specific string. The Excel file contains data. The below is what the data looks like. Sheet 1: Reference Number Some Header Some Header PRIMARY CODE 3545-0345843-640 Some Data Some Data SAMPLECODE 3545-4556577-640 Some Data Some Data ANOTHERCODE Sheet 2: Reference Number Some Header Some Header SECONDARY CODE 3545-0345843-640 Some Data Some Data THIRDCODE The macro would use Reference Number in sheet 2 to find the same reference number in sheet 1, if found, it would replace the primary code with the secondary code in sheet 2. After running the macro, sheet 1 looks like Sheet 1 (After macro): Reference Number Some Header Some Header PRIMARY CODE 3545-0345843-640 Some Data Some Data THIRDCODE 3545-4556577-640 Some Data Some Data ANOTHERCODE And the macro saves the Excel file in the same folder and append to the file name say " - after conversion" or something. The macro also needs to have some sort of validation mechanism to check whether the header is correct. If the header has changed, the macro will abort. Hope this is clear. Any questions please let me know. Thanks very much. Kind Regards, Jason