a question about extract item from sub-branch

ciao!!

i have 7 isocurves extracted on which i definite the points with a certain interval .and i hope that the 1st interpolated curve connecting the 1st point on the 1st isocurve, the 2nd point of the 2nd isocurve...till the  7th point of the 7th isocurve (of course wrapped). and  the 2nd interpolated curve connecting the 2nd point on the 1st isocurve, 3rd pint on the 2nd isocurve....till all the points finish.and if there are no enough points on one isocurve, that isocurve will be ignored. i know the extract branch item command, but it's not possible to extract every time one dfferent item from one different sub branch....... i thought that should must be the shortcut, hoping someone could indicate.......!

cos i was not able to creat a definition as above described, i simplified what i want  as 1st interpolated curve composed by all 1st points, 2nd interpolated curve composed by all 2nd points......i  weaved all the  points as in a single list firstly all the first points of all isocurves and secondly all the second points....but how can get 1st sub-branch as all of the 1st points of all the isocurve, then 2nd sub-branch as all of the 2nd points.......and then create interpolated curve from all the points of  each sub-branch???

i attached my definition, the form from which extracted the isocurves, and baked result(which is not at all what i want)  and wonder really someone here could give some suggestion!

thanks in advance!

cheers,

wei