did someone know how can i realize a double jump with this code?

Code:
	if (key_space)
{
if (distance_to_ground < 2)
{
distance_to_ground = 1;
player_dist.z = 5;
}
}

if (distance_to_ground > 0)
{
			
if (player_dist.z < (distance_to_ground * -1))
{
player_dist.z = distance_to_ground * -1;
				
}
}
else
{			
player_dist.z = -1 * distance_to_ground;
}