Can VBA draw user-defined lines on an Excel chart created? Pls help.

Yes it can.
But prgm it can be long winded.
Have a look @ ActiveSheet.Shapes.AddLine
and its methods & properties via F1 help in
the VBA editor.
I have done one (a while ago) that puts vector lines
from the centre of a XY scatter graph to various pts. If interested I can send you an example, but
be warned it can get complicated getting a reference
point etc for the graph.

Ivan