How can I open XMetal in default editor in Eclipse

[andre1987]

I am working with a team that develops an Eclipse RCP program. The program uses XML-files. When modifying xml-files we open them in XMetal configured by External Tools and file association in eclipse. Now we want to open XMetal directly in default editor. What I mean is that when I double-click an xml-file in package explorer, I want it will still open in XMetal but XMetal will appear in default editor in my active eclipse workbench, exactly in the same way as a word document does in eclipse.I will appropriate any kind of help