Escaping Parentheses in Excel

Question

I have an ASP.Net website that allows you to export a Gridview to Excel. The Gridview has some column headings with words and then numbers surrounded by parentheses like this:

Abc<br>(43)
Xyz<br>(55)

I have set the bound field's HtmlEncode property to False because I do not want it to escape the line break tags I have in there. This is fine and I can even use ( and ) to escape the parentheses if I need to.

The issue I'm having is that Excel looks at the (43) as a negative number and displays it as -43. How can I escape the parentheses?