The overflow error occurs because the date in a string format like "20240920", which is not directly convertible to a date using the Format function. You need to first convert this string to a valid date format before applying the Format function.

The correct script:

ExpDate = wsInput.Cells(i, "P").Value 

' Convert "YYYYMMDD" to date format 

dateValue = DateSerial(Left(rawExpDate, 4), Mid(rawExpDate, 5, 2), Right(rawExpDate, 2)) 

ExpDate = Format(dateValue, "M/D/YYYY")