Removing the sign from a double when displayed in a textblock

Is there any format string in the StringFormat property which can be used to remove the sign from a double when it is displayed in a TextBlock e.g.

<TextBlock Binding="{Binding SomeProp, StringFormat=0.####}" />

SomeProp would be a double but whether negative or positive I doon't want the sign to be shown.

Regards

Celestrium