How can i let a block do something when redstonesignal get in it?

Look at the vanilla Redstone blocks and learn from them.

OnNeighbohurChange (or similar name) Is called when one of adjacent blocks has changed somehow. In this case this includes redstone signal.

This works for me:

 

public void onBlockAdded(World worldIn, BlockPos pos, IBlockState state)
    {
        super.onBlockAdded(worldIn, pos, state);

    	if(worldIn.isBlockPowered(pos)) {
               //Do stuff
        } else {
               //Do other stuff
        }
    }

    /**
     * Called when a neighboring block changes.
     */
    public void onNeighborBlockChange(World worldIn, BlockPos pos, IBlockState state, Block neighborBlock)
    {
    	if(worldIn.isBlockPowered(pos)) {
               //Do stuff
        } else {
               //Do other stuff
        }
    }

Thank you