Ah ok, so todo get at handle of b-Spline first they have todo be animated. So make a go into sub-Edit Mode make a key at frame one with the handle.
Now open up the Graph editor go todo you Spline>object>máster and you should get a:
Vertex 1,2,3 etc.
Invec 1,2,3 etc.
Outvec 1,2,3 etc.
Where you can place expressions/scripts on. B-Spline handles have ODD tranform axis, they exist as only a point in space. And todo that sem todo have an inverted axis -y,x,-x. With my setup IM using an expression todo enlace the handle todo a point. Then driving that point with scripts/etc.
So all i do is first put a list controller on the invec/outvec/vertex, then on its avalible controller a point3 expression.
With the expression as IM not splitting its axis into thre, IM using a Vector. So the expression looks like :
[-a y, a, z,-a.x] .
a being a Vector name (you could call it anything), with a controller being the point. Now you ned a list controller because generally the handle never sits bang on the point and may Even fly of. So the list controller enables you todo align it.
Alos when you add this approach todo other vertex[s] the previous may get moved, so its best todo put the expression on everything your going todo control then align them all up with Whatever there being controlled point3 is for (x y, z) ive got some more tech on this ill have todo show you guys sometime ek.