Extracting Value from an expression

["L'Alchimista" <l.alchimista@xxxxxx>]

I'm trying to calculate the value of a trend line which angle is TLAng .
The problem : how can I extract the value XBar from the expression below ?

Inputs:TLAng(45);
Vars:XBar(3),LeftBar(1);

LeftBar=HighestBar(Osc,10);

ArcTangent( (Osc[XBar]-Osc[LeftBar]) / (LeftBar - XBar) ) = TLAng ;