SCSS: Add an if statement inside an Extend

Are there any chances to add a condition inside an extend?

I tried with the code below, but it seems not to work and I'm not sure that it's possible to do that.

Thank you in advance!

$frameWidthDesktop: 1920px;
$frameWidthMobile: 340px;

%frame {
  width: $frameWidthMobile;
  @if $frameWidthMobile == true {
    $frameHeight: 620px !global;
  }
  @else {$frameHeight: 800px !global;}
  height: $frameHeight;
}