OK

so i just did a mock up...... i havent tested this but just go through and do the corrections

ill test it now and adjust some parts (most likely) 

Function QueryData1(Src, OutputRange)

Dim Sht as Excel.WorkSheet

Dim cntStudConnection As ADODB.Connection

Set cntStudConnection = New ADODB.Connection
cntStudConnection.Provider = "Microsoft.Ace.OLEDB.12.0"
cntStudConnection.Open "C:\Users\Hala\Documents\BBB\Dummydata1.accdb"

Set rstNewQuery = New ADODB.Recordset
rstNewQuery.Open Source:=Src, ActiveConnection:=cntStudConnection

Set Sht = thisworkbook.Sheets.Add

Sht.Name = "TempSheet101"'<<--LET NAME THE SHEET HERE SO WE CAN DELETE IT EASY LATER

Sht.Range(OutputRange).CopyFromRecordset rstNewQuery

Set rstNewQuery = Nothing
cntStudConnection.Close
Set cntStudConnection = Nothing

End Function

Lets put your old code back and see whats what...

Private Sub CommandButton1_Click()
    Dim Sht as Excel.Worksheet <<-- ADD THIS
    Dim Username As String
    Username = TextBox9.Text
    Dim password As String
    password = TextBox10.Text
    
    Call Module1.QueryData1("SELECT [UserName], [Password] FROM [data]", OutputRange) '<<---PLACE THIS PART HERE

    Set Sht = Thisworkbook.Sheets("TempSheet101")    <-- ADD THIS, THIS IS THE NEW SHEET WITH THE DATA RIGHT!

    If IsNull(Me.TextBox9.Text) Or Me.TextBox9.Text = "" Then
        MsgBox "You must enter your username.", vbOKOnly, "Required Data"
        Me.TextBox9.SetFocus
        Exit Sub
    End If
     
    
    If IsNull(Me.TextBox10.Text) Or Me.TextBox10.Text = "" Then
        MsgBox "You must enter your Password (case sensitive).", vbOKOnly, "Required Data"
        Me.TextBox10.SetFocus
        Exit Sub
    End If
     
    
    Dim temp As String
     On Error Resume Next
     temp = WorksheetFunction.VLookup(Me.TextBox9.Value, Sht.usedRange, 1, 0)' <<-- ADD THE SHEET HERE TOO
 
If Username = temp Then
     
    Err.Clear
    temp = ""
    temp = WorksheetFunction.VLookup(Me.TextBox9.Value, Sht.UsedRange, 2, 0) '<<--AND HERE
    On Error GoTo 0
    If password = temp Then
        'Sheets("ADMIN").Visible = xlSheetVisible              '<<-- I COMENTED A COUPLE OF LINES HERE
        MsgBox "Password & Username Accepted"
        Unload Me
        'Sheets("ADMIN").Select
        'Range("A1").Select
    Else
        'Sheets("ADMIN").Visible = xlVeryHidden
        MsgBox "Username & Password Combination Not Accepted, Workbook will close"
        Unload Me
            
        End If
    End If
     



End Sub

just work with this for now........ these lookups i dont think will work correctly just yet.... im not used to using excels lookups just give me a minute to test this out......