Display an error message based on particular condition

Hi guys

When the whole row in excelsheet is full for particular date that means all the values of columns (Legal Charge,GA and DNM) have been entered for particular date then display an error message if the another user tries to enter the values for the same date .
It means the user can enter the values for same date only if values of Legal Charge,GA and DNM are empty,otherwise an error message should pop up.

Private Sub CommandButton1_Click()

  Dim iR As Long
  Dim ws1 As Worksheet
  
    Set ws1 = Worksheets("sheet2")
    
      With ws1
Set i = .Columns(1).Find(What:=DateValue(ComboBox1.Value), LookIn:=xlValues, LookAt:=xlWhole, SearchOrder:=xlByRows, SearchDirection:=xlNext, MatchCase:=False, SearchFormat:=False)
              If i Is Nothing Then
           iR = .Cells(Rows.Count, 1).End(xlUp).Offset(1, 0).Row
        Else
           iR = i.Row
        End If
        
        .Cells(iR, 1).Value = Format(ComboBox1.Value, "mm/dd/yyyy")
        .Cells(iR, 2).Value = Format(Now, "hh:mm")
        .Cells(iR, 3).Value = Application.UserName
       
          If ComboBox2.Value = "Legal Charge" Then
             .Cells(iR, 4).Value = Me.TextBox1.Value
             .Cells(iR, 5).Value = Me.TextBox3.Value
          ElseIf ComboBox2.Value = "DNM" Then
             .Cells(iR, 6).Value = Me.TextBox1.Value
             .Cells(iR, 7).Value = Me.TextBox3.Value
             .Cells(iR, 8).Value = Me.TextBox2.Value
          Else
             .Cells(iR, 9).Value = Me.TextBox1.Value
             .Cells(iR, 10).Value = Me.TextBox3.Value
             .Cells(iR, 11).Value = Me.TextBox2.Value
          End If
      End With
      
End Sub

Can anyone please figure out my problem.

Thanks
Aman