Extending a slur back from end of repeat

[Stephen Martin]

Does anyone have a suggestion for making a slur which returns
 from notes at the end of a repeat back to notes at the 
beginning of the repeat?

The ends should look like a slur which spans a line break,
 i.e. the start of the slur ends at the double bar lines,
the end of the slur comes in at the beginning of the repeat
block.

I tried changing x-extent and extend-x-extent of a local
slur to achieve the desired appearance, but to no avail..

thanks, Steve