Auto Filtering Blanks

FatManFluff 

If you want Excel to find automatically the row in the "Check In" column based on the "Check Out" entry, you can maybe use the MATCH and INDEX functions.

=IFERROR(INDEX($A$2:$A$100, MATCH(A2, $B$2:$B$100, 0)), "")

Or a VBA Macro for Auto-Matching Scanned Entries

Insert this VBA code into the worksheet where your "Check Out" and "Check In" columns are located.

Private Sub Worksheet_Change(ByVal Target As Range)
    Dim checkOutRange As Range
    Dim checkInRange As Range
    Dim checkOutCell As Range
    
    ' Define the range of "Check Out" and "Check In" columns
    Set checkOutRange = Me.Range("A2:A100") ' Adjust range as needed
    Set checkInRange = Me.Range("B2:B100")   ' Adjust range as needed
    
    ' Check if the change was made in the "Check In" column
    If Not Intersect(Target, checkInRange) Is Nothing Then
        ' Loop through the Check Out column to find a match
        For Each checkOutCell In checkOutRange
            If checkOutCell.Value = Target.Value Then
                ' Match found, place the value in the corresponding "Check In" row
                Target.Value = checkOutCell.Value
                Exit For
            End If
        Next checkOutCell
    End If
End Sub

This code runs every time a value is entered in the "Check In" column.

Don’t forget to save your workbook as a macro-enabled workbook (.xlsm) to ensure the macro is saved.

My answers are voluntary and without guarantee!

Hope this will help you.