Growing lines, how?

hi, i’m driving crazy with this, i just want to do a simple line grow from a point.
i tried with free transform, but it scales it from the middle of the line(so i have to move it back to its position, but that’s difficult), i want it to grow from a extreme of the line (i don´t know if i make myself clear)
i tried also with a mask, but that means creating another layer and another element, and i have many lines, that would be too much work.
it seems so simple!!!
how can i make a line grow from a point(the easy way)??? :crying:
help please!!!