Excel interop prevent showing password dialog

I am writing a program to clean excel files from empty rows and columns, i started from my own question Fastest method to remove Empty rows and Columns From Excel Files using Interop and everything is going fine.

The problem is that i want to prevent excel from showing the password dialog when the workbook is password protected and to throw an exception instead of that.

i am using the following code to open excel files using interop:

 m_XlApp = New Excel.Application
 m_XlApp.visible = False
 m_XlApp.DisplayAlerts = False

 Dim m_xlWrkbs As Excel.Workbooks = m_XlApp.Workbooks
 Dim m_xlWrkb As Excel.Workbook
 m_xlWrkb = m_xlWrkbs.Open(strFile)

 m_xlWrkb.DoNotPromptForConvert = true          

i tried to pass an empty password as some links suggested

m_xlWrkb = m_xlWrkbs.Open(strFile, Password:="")

Or using

m_xlWrkb.Unprotect("")

but no luck.

any suggestions?