Open Excel file for reading with VBA without display

Not sure if you can open them invisibly in the current excel instance

You can open a new instance of excel though, hide it and then open the workbooks

Dim app as New Excel.Application
app.Visible = False 'Visible is False by default, so this isn't necessary
Dim book As Excel.Workbook
Set book = app.Workbooks.Add(fileName)
'
' Do what you have to do
'
book.Close SaveChanges:=False
app.Quit
Set app = Nothing

As others have posted, make sure you clean up after you are finished with any opened workbooks

Using ADO (AnonJr already explained) and utilizing SQL is possibly the best option for fetching data from a closed workbook without opening that in conventional way. Please watch this VIDEO.

OTHERWISE, possibly GetObject(<filename with path>) is the most CONCISE way. Worksheets remain invisible, however will appear in project explorer window in VBE just like any other workbook opened in conventional ways.

Dim wb As Workbook

Set wb = GetObject("C:\MyData.xlsx")  'Worksheets will remain invisible, no new window appears in the screen
' your codes here
wb.Close SaveChanges:=False

If you want to read a particular sheet, need not even define a Workbook variable

Dim sh As Worksheet
Set sh = GetObject("C:\MyData.xlsx").Worksheets("MySheet")
' your codes here
sh.Parent.Close SaveChanges:=False 'Closes the associated workbook

Open them from a new instance of Excel.

Sub Test()

    Dim xl As Excel.Application
    Set xl = CreateObject("Excel.Application")

    Dim w As Workbook
    Set w = xl.Workbooks.Add()

    MsgBox "Not visible yet..."
    xl.Visible = True

    w.Close False
    Set xl = Nothing

End Sub

You need to remember to clean up after you're done.

In excel, hide the workbooks, and save them as hidden. When your app loads them they will not be shown.

Edit: upon re-reading, it became clear that these workbooks are not part of your application. Such a solution would be inappropriate for user workbooks.