UIButton grid activate same time dragging

Question

I have a grid of various UIButtons (5 x 5)... Now I have a UIControlEventTouchUpInside.. this means that when the user wants to choose various buttons need to press each, one by one...

How can I do to activate the buttons when the user is dragging his finger over various buttons.

Here is the code I use:

for (i = 0; i < num_caselles; i++) 
{
   lletra = [[UIButton alloc] initWithFrame:CGRectMake(POS_H, POS_V, mida_boto, mida_boto)];
   [botones addObject: lletra];
   [lletra setTitle: [caselles objectAtIndex: i] forState: UIControlStateNormal];
   lletra.tag = i; 
   [lletra addTarget:self action:@selector(lletraPitjada:) forControlEvents: UIControlEventTouchUpInside];
}

Answer 1

Ok finally I resolved this way :

-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [[event touchesForView:self] anyObject];
    CGPoint location = [touch locationInView:touch.view];


    for(UIButton*boton in botones) 
    {
    if(CGRectContainsPoint([boton frame], location) && boton.tag != boton_anterior) 
    { 
       boton_anterior = boton.tag;
       [self lletraPitjada:boton];
    }
    }

}   

I override/commented the button set action, because is not working for me :

//[lletra addTarget:self action:@selector(lletraPitjada:) forControlEvents: UIControlEventTouchDragEnter];

and deactive user interaction, because UITouch dont like buttons :

lletra.userInteractionEnabled = NO;

And voilà... all is working perfect...