Lighten Hair Color Without Losing Dimension?

I want to get my hair lightened at a salon, but I already have several natural and chemical highlights. My hair is dark blonde/light brown and I want to go to more of a Lauren Conrad blonde or just a couple shades lighter. With that being said, is there any way I can get that done without highlighting (I don't want my hair to look streaky) and without dying (if I dye then the dimensions from the highlights will go away). I just want to overall lighten. Thank you!