superspammer

Hi! I'm italian so i'll try to write understendable.
I've a little problem: I have some sprites for standing player, and for walking player but when i change the player remains firm.
So i've tried to work on it,but... nothing XD.
Please help me.I'll post the script i use so you can help me. I HAVEN'T WROTE this code,i've founded it on the site.

if !place_meeting(x,y+1,obj_block) // if we are in the air
{
grav = .5; // set the gravity to .5
vspd += grav; // add .5 to our vspd once every step
}
else // else if we are on the ground
{
grav = 0; // set the gravity to 0
vspd = 0; // set vspd to 0 to stop moving
if keyboard_check_pressed(vk_up) // since we are on the ground, we can handle jumping here, so check if we pressed up
{
vspd = -8; // set the vspd to -8, which will make us jump
}
}
if keyboard_check_released(vk_up) // if we released the up button while in the in air
{
vspd *= .5; // divide our vspd by 2, creating a smooth type of variable jumping
}
if vspd > 8 // we don't want to fall too fast, so lets limit our vspd
{
vspd = 8; // note that if you want to be able to fall fast, you can remove this without affecting the code (but I wouldn't)
}
repeat(abs(vspd)) // we want to check for a collision every pixel, so we use a repeat() function to check every pixel while falling
{
if !place_meeting(x,y+sign(vspd),obj_block) // vspd can be negative or positive, so we check 1 pixel above or below, depending on which direction we are going
{
y += sign(vspd); // add to our y value 1 pixel at a time, letting use check for a collision every pixel
}
else // else if we hit a block
{
vspd = 0; // stop moving vertically
}
}
hspd = (keyboard_check(vk_right)-keyboard_check(vk_left))*4; // a nice little trick that will set our hspd to +4 or -4 depending what button we are holding
repeat(abs(hspd)) // same as the vspd, we want to check for a collision at every pixel we move
{
if !place_meeting(x+sign(hspd),y,obj_block) // if there is no block to our left or right
{
x += sign(hspd); // add to our x value depending on which way we are going
}
}

For change the script i used the drag'n drop action. Example: Left button pressed- change sprite to sprite_left_walk and Left button released- change sprite to sprite_left_stand

THANKS A LOT IF YOU HELP ME.