Adding Password to Modify with and without Password to Open

[AC PORTA VIA]

If I am using line #1 below to add password to open than I can use line #2 for password to modify
why can't I use just line to add password to modify without password to open?
'line1 password to open

.Password = Workbooks("MY WORKBOOK.xlsm").Sheets("TEST").Cells(I, 6).Value

'line#2 password to modify

.Protect Password:=Workbooks("MY WORKBOOK.xlsm").Sheets("TEST").Cells(I, 7).Value