One way to do it:
One table with the fields EmployeeID (Unique Number) and Account Name. All your employee Records, of course, must have an ID.
So at login you could run a script looking up the ID in that table. Now you get the ID and can look up your staff records with the ID and display whatever you have to display.
If you don't have given unique IDs to your human Resources then I don't know.... but I am sure you have....
Here's an example of the script that Erna Meierdierks has recommended:
Go to Layout ["Employees" (Employees)]
Enter find mode  --> clear the pause check box
Set field [ Employees::AccountName ; Get ( AccountName ) ]
Perform Find 
Set Variable [$$EmployeeID ; Employees::EmployeeID ]---> Put the ID in a global variable to make it accessible throughout the file
Here's a second option:
Go to Layout ["Dashboard" (Main) ]
Set Field [ Main::gAccountName ; Get ( AccountName ) ]
With the second option, gAccountName is a global field that you can use to link to the Employees table in a relationship as well as to other tables that include an Account Name field. (A text field can be set up to auto-enter an account name when the record is first created and is often used to "mark" which records "belong" to a given user. Record Level Access can even be set up in Manage | Security to prevent users from viewing and/or editing records for which their account name does not appear in such a field.)