erm i have read through all the post about erasing line.. and this is what i did...

After i draw the line, a dialog appear and after OnOk,
i set SetROP2 to R2_NOP and draw the line in same position.. but the line is still there. I have tried a number of flags for the SetROP2 but it has no effect.

I even tried to create a CPen with same background color and draw the line, it doesn works either.

Anyone knows where do i go wrong?