Help !Enter ID>>auto search for blank cell>>prevent closing of excel>>re-enter ID to close

The ideas is to prompt out a input box that ask the user to key in ID, number only value. then it will auto search for a first blank cell founded in column H to allow the barcode enter from there. while the user is key in the barcode away from the PC using Bluetooth barcode scanner, the excel must not close by others user. to close it, user must enter the same ID The code only work until the enter value is true then it wont select the cell