select clienti where data BETWEEN @Data1 And  @Data2
Dim Data1 as Date=Date.Today
Dim Data2 as Date=Date.Today.AddMonths(1)
TuoCommand.Parameters.Add(New Parameter With {.DbType=DbType.DateTime, .Value=Data1,.ParameterName="@Data1"})
TuoCommand.Parameters.Add(New Parameter With {.DbType=DbType.DateTime, .Value=Data2,.ParameterName="@Data2"})