Hi Dean,
Here are the steps and some images to help. Please let me know if I missed anything. Also - see if these steps answer the additional part about arcs.
- Draw 100mm rectangle.
- Now draw the line using your instructions below.
" draw a line 10mm up from the bottom right hand corner to 20mm in from the top RH corner"
- Now add the dimensions.
NOTE: After starting the dimension command, you can select end points to place dimensions.
((Since you specified "end points" that is what I selected for dimension placement))
This should give you the precise placement for the end point of the line you want.
Let me know if I need to explain anything in more detail.
Thanks,
Andy