Carriage Return in filtered Text Box

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ASP.NET

Ajax

I have:

<asp:TextBox ID="txtRemarks" runat="server" Height="165px" Width="325px" MaxLength="250" Rows="5" TabIndex="15" Wrap="True" TextMode="MultiLine"  />
<ajaxToolkit:FilteredTextBoxExtender ID="ftbetxtRemarks"  runat="server" TargetControlID="txtRemarks" FilterType="Custom, LowercaseLetters, UppercaseLetters, Numbers" FilterMode="ValidChars" ValidChars=" -,." />

I would like the user to be able to press enter (return) and the cursor in the textbox go to another line. The filter is preventing this. Is there a better way to do this, or is this not possible?