Adding Columns in a Gridview

Question

Hi all.

 

I hope someone can help me.

 

I have a gridview with 6 Columns. Firstly I added the sixth using a template field "Available".

 

<Columns>

<asp:BoundField DataField="ITNOLQ" HeaderText="Item Number" SortExpression="ITNOLQ" />

<asp:BoundField DataField="WHLCLQ" HeaderText="Location" SortExpression="WHLCLQ" />

<asp:BoundField DataField="QLOHLQ" HeaderText="Quantity" SortExpression="QLOHLQ" />

<asp:BoundField DataField="QLALLQ" HeaderText="Allocated" SortExpression="QLALLQ" />

<asp:BoundField DataField="ORDRLQ" HeaderText="Order Number" SortExpression="ORDRLQ" />

<asp:TemplateField HeaderText="New Count" ItemStyle-HorizontalAlign="Center" >

<ItemTemplate>

<asp:TextBox ID="Available" Width="20" runat="server" />

</ItemTemplate>

</asp:TemplateField>

</Columns>

 

Simply I wish to do a sum QLOHLQ - QLALLQ and display that in the Available template field.

 

I have trawled the web and there seem to be a miriad of ways of doing this and I'm at the point of confusion.

 

Could someone possibly help me please?