How to get VBA Data Validation pop-up message if cell in named range is empty

Hi all - VERY new to VBA and Macros; any help you can give me is appreciated! This seems so simple but is not working for me...

I am trying to get a pop-up message "Please answer all questions" IF any cell in named range "Responses" is empty
If not will run remaining Submit_Responses macro

Current Macro:
Sub Submit_Responses()
'
' Submit_Responses Macro
'
    Range("K25:L26").Select
    With Selection.Font
        .ThemeColor = xlThemeColorAccent4
        .TintAndShade = 0
    End With
    Range("A1").Select
End Sub

~ Thank you in advance!!