You can selectively make objects move when the time scale is 0 with the "set object time scale" system action. Then you can use the Sprite.dt expression to get dt.
For example if you have a sprite with the sine behavior.
This would pause everything else besides the sprite.
system: set time scale to 0
system: set sprite time scale to 1.0
every tick:
Text: set text to sprite.dt]start of layout:
system: set time scale to 0
system: set sprite time scale to 1.0
every tick:
Text: set text to sprite.dt