how to fix some column size width in gridview?

Question

this is my gridview page i need fix to 'RBL GL NAME ' this column fix the size . kindly tell me. 

 

 

 

this is my code:

 

<asp:GridView ID="XbrlGLGrid" runat="server" Width="500px" AutoGenerateColumns="False" onrowdatabound="XbrlGLGrid_RowDataBound">

<HeaderStyle CssClass="header" Height="15px" Width="100px" />

<FooterStyle CssClass="smallheader" />

<RowStyle CssClass="smallnavy" />

<Columns>

<asp:BoundField HeaderText="Col.No." DataField="ColNo" ItemStyle-Width="30px" HeaderStyle-Width="100px"/>

<asp:BoundField DataField="ElementName" HeaderText="RBI GL Name" ItemStyle-Horizontal ItemStyle-Width="40px" HeaderStyle-Width="100px"/>

<asp:TemplateField HeaderText="GL Code" ControlStyle-BorderWidth="1px" ItemStyle-Horizontal ItemStyle-Width="100px" HeaderStyle-Width="90px">

<ItemTemplate>

<asp:TextBox ID="txtGLCode" runat="server" CausesValidation="false" CssClass="tooltip" Width="100px" EnableViewState="true"

ToolTip="For Help, Double Click or Press F2" AutoCompleteType="Disabled" AutoPostBack="True"

OnTextChanged="txtGLCode_TextChanged"></asp:TextBox>

</ItemTemplate>

<ControlStyle BorderWidth="1px" BorderColor="Silver" />

</asp:TemplateField>

<asp:BoundField DataField="GlCode" HeaderText="Mapped GL Codes" ItemStyle-Horizontal ItemStyle-Width="200px" HeaderStyle-Width="100px"/>

<asp:BoundField DataField="Amount" HeaderText="Value" ItemStyle-HorizontalAlign="Right" ItemStyle-Width="100px" HeaderStyle-Width="110px" />

<asp:BoundField HeaderText="Enable" DataField="Enable" ItemStyle-CssClass="hiddencol" HeaderStyle-CssClass="hiddencol"/>

</Columns>

</asp:GridView>