The RSAT doesn't have any roll back feature. So, it can be frustrating updating the excel file with unique records. Well not to worry - RSAT supports Excel formulas. The user guide suggests using RandBetween(a,b) Excel function. However, that isn't really reliable and you are hoping you don't get the same random number. I have been using date formula. The below concatenates the datetime to the string. =CONCATENATE("SS",TEXT(NOW(),"yymmddhhmmss")) If you want to get started with RSAT. Download the tool and the user guide from here. https://www.microsoft.com/en-us/download/details.aspx?id=57357 You can also watch a short video that walks you through how to use it.