tekushee_vremya = Now()
   vremya_c_30_sek = tekushee_vremya + Second(30)

 If Now() < tekushee_vremya Then

tekushee_vremya = Now()

 vremya_c_30_sek = tekushee_vremya + 30/86400(тут у Вас тоже была ошибка)
 If Now() < vremya_c_30_sek Then
...

Sub proverka_plusov()
    vremya_c_30_sek = tekushee_vremya + 30 / 86400
    If Now() < vremya_c_30_sek Then
      'Что-то выполняется
 MsgBox "если истина"
 Else
 ' Что-то не выплняется
 MsgBox "если не истин"
 End If

Sub www()
    Dim a As Range
    For Each a In Range("I1", Cells(Rows.Count, "I").End(xlUp)).SpecialCells(12).Areas
        a.Value = Application.Trim(a.Value)
    Next
End Sub

If Environ("USERNAME") <> "Nikolay" Or Environ("USERNAME") <> "Ivan"  Then

If Environ("USERNAME") <> "Nikolay" and Environ("USERNAME") <> "Ivan"  Then

Private Sub Worksheet_Calculate()
    If Me.AutoFilter.Filters(3).On Then
        If Worksheets("Лист1").AutoFilter.Filters(3).Criteria1 = "=0" Then Cells(1, 3) = ""
        If Worksheets("Лист1").AutoFilter.Filters(3).Criteria1 Like "*20*" Then Cells(1, 3) = "Много"
        If Worksheets("Лист1").AutoFilter.Filters(3).Criteria1 Like "*15*" Then Cells(1, 3) = "Нормально"
        If Worksheets("Лист1").AutoFilter.Filters(3).Criteria1 Like "*10*" Then Cells(1, 3) = "Мало"
        Exit Sub
    End If
    Cells(1, 3) = ""
End Sub

If Worksheets("Лист1").AutoFilter.Filters(3).Criteria1 = "=0" Then Cells(1, 3) = ""