How do you highlight just part of someones reply? 

if you mean like this ??

you click your mouse and move over the bit you want as if you were going to copy - it highlights  blue and you then click the B bold button 

I quote the whole post and delete the bits i don't want to re-post, there may be another way, but i haven't found it

I did it, i did it  Thank you Mrs H 

*whacks Rawky* 

I did it, i did it  Thank you Mrs H