Error message to pop up if all fields haven't been completed

Hi, I want to write something which says if any of the grouped radio buttons have been left blank - i.e. you need to select at least one in each group, then when you click on the 'create' button at the bottom you get a pop up error saying "Incomplete form" or something, forcing the user to complete all fields before the document is produced. I've put my full Script below FYI which is working on it's own, not sure where I would need to put this new bit either as it needs to pop up after they try to submit and I probably need to say if all fields have been completed correctly then carry on with this below. Any help would be much appreciated.

Option Explicit

Private Sub CommandButton1_Click()


Dim wapp As Word.Application
Dim wdoc As Word.Document
If Me.OptionButton1 = True Then
Set wapp = CreateObject("Word.Application")
Set wdoc = wapp.Documents.Open("\\emea.ajgco.com\emeadata\vol1\SoDaN Test\Gallagher\PI Sodan Advised AJG Wholesale1.dotx")
wapp.Visible = True
ElseIf Me.OptionButton2 = True Then
Set wapp = CreateObject("Word.Application")
Set wdoc = wapp.Documents.Open("\\emea.ajgco.com\emeadata\vol1\SoDaN Test\Gallagher\PI Sodan Advised AJG1.dotx")
wapp.Visible = True
End If

If Me.OptionButton3 = True Then
wapp.Selection.Goto what:=wdGoToBookmark, Name:="NewRenewal"
wapp.Selection.TypeText Sheet2.Range("b15")
ElseIf Me.OptionButton4 = True Then
wapp.Selection.Goto what:=wdGoToBookmark, Name:="NewRenewal"
wapp.Selection.TypeText Sheet2.Range("b16")
End If

wapp.Selection.Goto what:=wdGoToBookmark, Name:="Insured"
wapp.Selection.TypeText ActiveSheet.TextBox2

wapp.Selection.Goto what:=wdGoToBookmark, Name:="Type1"
wapp.Selection.TypeText ActiveSheet.ComboBox1

wapp.Selection.Goto what:=wdGoToBookmark, Name:="Type2"
wapp.Selection.TypeText ActiveSheet.ComboBox1

wapp.Selection.Goto what:=wdGoToBookmark, Name:="Type3"
wapp.Selection.TypeText ActiveSheet.ComboBox1

wapp.Selection.Goto what:=wdGoToBookmark, Name:="Insurer"
wapp.Selection.TypeText ActiveSheet.ComboBox2

If Me.OptionButton9 = True Then
wapp.Selection.Goto what:=wdGoToBookmark, Name:="AddOns"
wapp.Selection.TypeText Sheet2.Range("b2")
ElseIf Me.OptionButton10 = True Then
wapp.Selection.Goto what:=wdGoToBookmark, Name:="AddOns"
wapp.Selection.TypeText Sheet2.Range("b3")
End If

If Me.OptionButton5 = True Then
wapp.Selection.Goto what:=wdGoToBookmark, Name:="MarketStrategy"
wapp.Selection.TypeText Sheet2.Range("b11")
ElseIf Me.OptionButton6 = True Then
wapp.Selection.Goto what:=wdGoToBookmark, Name:="MarketStrategy"
wapp.Selection.TypeText Sheet2.Range("b12")
End If


If Me.OptionButton7 = True Then
wapp.Selection.Goto what:=wdGoToBookmark, Name:="PenInvolvement"
wapp.Selection.TypeText Sheet2.Range("b8")
ElseIf Me.OptionButton8 = True Then
wapp.Selection.Goto what:=wdGoToBookmark, Name:="PenInvolvement"
wapp.Selection.TypeText " "
End If

If Me.OptionButton11 = True Then
wapp.Selection.Goto what:=wdGoToBookmark, Name:="BinderNonBinder"
wapp.Selection.TypeText Sheet2.Range("b20")
ElseIf Me.OptionButton12 = True Then
wapp.Selection.Goto what:=wdGoToBookmark, Name:="BinderNonBinder"
wapp.Selection.TypeText Sheet2.Range("b19")
End If

If Me.OptionButton13 = True Then
wapp.Selection.Goto what:=wdGoToBookmark, Name:="DaNFullyMet"
wapp.Selection.TypeText Sheet2.Range("b5")
ElseIf Me.OptionButton14 = True Then
wapp.Selection.Goto what:=wdGoToBookmark, Name:="DaNFullyMet"
wapp.Selection.TypeText Sheet2.Range("b6")
End If

If ActiveSheet.TextBox3 = "" Then
GoTo ContinueNext
Else
wapp.Selection.Goto what:=wdGoToBookmark, Name:="CommentsOnNotMeetingNeeds"
wapp.Selection.TypeText ActiveSheet.TextBox3
End If

ContinueNext:
If ActiveSheet.TextBox3 = "" Then
wapp.Selection.Goto what:=wdGoToBookmark, Name:="CommentsOnNotMeetingNeeds"
wapp.Selection.TypeText " "
End If


End Sub

Private Sub OptionButton5_Click()

End Sub