In trapezoid $$ABCD$$, leg $$\overline{BC}$$ is perpendicular to bases $$\overline{AB}$$ and $$\overline{CD}$$, and diagonals $$\overline{AC}$$ and $$\overline{BD}$$ are perpendicular. Given that $$AB=\sqrt{11}$$ and $$AD=\sqrt{1001}$$, find $$BC^2$$.

(第十八届AIME2 2000 第8题)