Public Sub fnQryPer(intPer As Integer, intMonth As Integer, intYear As Integer)
Dim intCountDay As Integer
Dim strSQL As String

Select Case intPer
 Case  1 
 strSQL =  "WHERE myFieldDate BETWEEN #"  & intMonth &  "/1 /" & intYear & _
               "# AND #"  & intMonth &  "/15 /" & intYear &  "#;" 
 Case  2 
'количество дней в месяце
 intCountDay = Day(DateSerial(Year(DateSerial(intYear, intMonth,  32 )), Month(DateSerial(intYear, intMonth,  32 )),  0 ))

 strSQL =  "WHERE myFieldDate BETWEEN #"  & intMonth &  "/16 /" & intYear & _
               "# AND #"  & intMonth &  "/"  & intCountDay &  "/"  & intYear &  "#;" 
End Select

strSQL =  "SELECT * FROM MyTabl "  & strSQL
CurrentDb.QueryDefs( "МойЗапрос" ).SQL = strSQL
DoCmd.OpenQuery  "МойЗапрос" 
End Sub