Fieldset padding from another fieldset

My project looks like this

Screenshot

As you see i have placed 2 fieldsets one next to other.

Lets now see the CSS code

#map{
  padding-left: 400px;
}

Dont mind about the 'map', it is the id of the div at the second fieldset.

If im padding 50 or 100 or even 200 pixels it won't move because it is padding from the right side of screen .

My goal is to make the right fieldset padding from the left one and not from the left side of the website.

Is there any way to make the end of the first fieldset , the start of the right?

I want my padding to be accurate , thanks in advance!