Result:

Option Explicit
Sub Checks()

    Dim myNames As Variant
    Dim wkbk As Workbook
    Dim myPath As String
    Dim iCtr As Long
    
    MsgBox "Select the SystmOne GMS Files (Originals)", vbInformation
    
    With Application.FileDialog(msoFileDialogFolderPicker)
        ' Optional: set folder to start in
        .InitialFileName = "C:\my documents\excel\"
        .Title = "Select the folder to process"
        If .Show = True Then
            myPath = .SelectedItems(1)
            'add trailing backslash
            myPath = myPath & "\"
        Else
            MsgBox "Try later!"
            Exit Sub
        End If
    End With
    
    myNames = Array("WORKBOOKONE.xls", _
                    "WORKBOOKEIGHT.xls", _
                    "WORKBOOKNINE.xls")    
    
    For iCtr = LBound(myNames) To UBound(myNames)
        Set wkbk = Nothing
        On Error Resume Next
        Set wkbk = Workbooks.Open(Filename:=myPath & myNames(iCtr))
        On Error GoTo 0
        
        If wkbk Is Nothing Then
            MsgBox myPath & myNames(iCtr) & " was not opened!" & vbLf & _
                "Maybe it doesn't exist???"
        Else
            'do stuff with wkbk
            MsgBox wkbk.Worksheets(1).Range("a1").Text
            wkbk.Close savechanges:=False 'or true??
       End If
    Next iCtr

End Sub