Help with validating length of data entered

Hello,

I am usin the code below to make sure users enter all data in MaskedInput control, but when the user enters only one number a the end, for example ___,___9, the "Invalid" error message  does not trigger. How do i fix this problem?

function C1RotationMin_OnClientBlur(sender, e) {

                var mskinput = $find('<%=C1RotationMin.ClientID %>');
                var txb = $('#C1RotationMin_C1TextBox');
                if (mskinput.get_text().trimEnd().length < 6 && mskinput.get_text().trimEnd().length > 0) {
                    alert("Invalid");
                    document.focus();
                    mskinput.focus();

                }

            };

<td class="style40" bgcolor="Silver" >
                        <cc2:C1MaskedInput ID="C1RotationMin" runat="server" Mask="999,999"
                            Width="50px" style="top: 0px; left: 0px" OnClientBlur="C1RotationMin_OnClientBlur" OnClientFocus="C1RotationMin_OnClientFocus"/>
                           
                    </td>



Thanks,

Victor