Custom Error Message in Hyperlink field of the Griview

Question

hi Experts I have the following code on my gridview in an aspx page

<asp:HyperLinkField  DataNavigateUrlFields="ProposalPath" DataTextField="ProposalPath" DataTextFormatString="View Proposal" Target="_blank"  />
                                <asp:BoundField DataField="ProposalPath" HeaderText="ProposalPath" ReadOnly="True" SortExpression="ProposalPath" Visible="False" />

I have binded the gridview to a sql datasource and when the user clicks the hyperlink field in the gridview a document would open if its a valid url .If it is a invalid url the error message would pop up saying
"Cannot find file: url ,Make sure the path or internet address is correct."

My Requirement is to amend the error message to a custom error message by using some script or any way possible.

Please Suggest .

Thank you