I'm currently developing a user control, which is in sore need of some styling. So I'm trying to figure out how to extend the Umbraco backend with some styling. 

First I tried to insert the styles I needed in the stylesheet configured for use by the Rich Text Editor, counting on this stylesheet being loaded by the Umbraco backend, but a closer scrutiny revealed that this was not the case.

I tried adding the stylesheet from code like this:

var stylesheetLiteral = new LiteralControl();
stylesheetLiteral.Text = @"<link href=""/css/umbextras.xss"" type=""text/css"" rel=""stylesheet"" />";
Pager.Header.Controls.Add(stylesheetLiteral);

But no dice. I guess the /umbraco/editContent.aspx page doesn't have a hader section with runat="server".

I could off course add the styles to one of the stylesheets included in the Umbraco source code, but that would make my usercontrol vulnerable in future umbraco updates.

Does anyone know of a safe way to do this?

Regards
.Hauge