How To Add To An Existing Random File

Im creating a login system that allows staff to clock in using a 5 digit code. Staff members can also use the "add an employee" function to add a new employee to the Random File.The problem is, everytime i try to create a new employee and hit the save button, the new record writes over the existing records, one by one, everytime the programme is stopped and started up again.

My Question is: How can i get the new record to be saved, without deleting existing records,

Here is the save buttons click method:FileOpen(fileNumber, "C:employee.dat", OpenMode.Random, OpenAccess.Write) 'open the file with Write Access
myEmployee.name = txtNewName.Text 'adds the name
myEmployee.id = txtNewID.Text 'adds the ID
FilePut(fileNumber, myEmployee, n) 'save to the file
FileClose(fileNumber)