You can turn your item columns into TemplateColumns and do the following which will localize your code to the control level and you don't have to worry about all the searching. I pefer to never use the built in column types because there are usually future enhancements that require changing the columns to TemplateColumns anyways. It also gives you a lot of flexibiltiy on useage.

Here is an example:

<asp:GridView ID="grdYourGrid" runat="server" AutoGenerateColumns="False">
    <Columns>
        <asp:TemplateField HeaderText="YourField1">
            <ItemTemplate>
                <asp:Literal runat="server" ID="ltYourField1" 
                    OnDataBinding="ltYourField1_DataBinding" />
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="YourField2">
            <ItemTemplate>
                <asp:Literal runat="server" ID="ltYourField2" 
                    OnDataBinding="ltYourField2_DataBinding" />
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="YourCheckBoxField">
            <ItemTemplate>
                <asp:CheckBox runat="server" ID="chkYourCheckBoxField" 
                    OnDataBinding="chkYourCheckBoxField_DataBinding" />
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>

Then in your codebehind implement each control's OnDataBinding:

protected void ltYourField1_DataBinding(object sender, System.EventArgs e)
{
    Literal lt = (Literal)(sender);
    lt.Text = (bool)(Eval("YourCheckBoxField")) ?
        "##########" : Eval("YourField1");
}

protected void ltYourField2_DataBinding(object sender, System.EventArgs e)
{
    Literal lt = (Literal)(sender);
    lt.Text = (bool)(Eval("YourCheckBoxField")) ?
        "##########" : Eval("YourField2");
}

protected void chkYourCheckBoxField_DataBinding(object sender, System.EventArgs e)
{
    CheckBox chk = (CheckBox)(sender);
    chk.Checked = (bool)(Eval("YourCheckBoxField"));
}

The advantages to doing it this way is your could replace code easily as it is all isolated and has no 'searching' for expected controls. I very rarely use the RowDataBound event because it makes you have to write specific code to look for the controls and it makes more sense to me to have the code localized to the control. If someone changes something they know there are ONLY affecting that one control instead of everything on the row possibly as a side effect. You could also use the <%# method and do the Evals right in the markup but I personally prefer to never have any code in the aspx markup at all.