I have a Windows forms PropertyGrid and a customer UITypeEditor per http://msdn.microsoft.com/en-us/library/system.drawing.design.uitypeeditoreditstyle.aspx
Long story short, you can't. The basic MS PropertyGrid does not allow you to customize this text. It even uses a bitmap with 3 dots instead of text anyway and the width of the control is fixed.
Disclaimer: I'm the developer behind Smart PropertyGrid.Net, which can do what you want to achieve.