Adding a border around a sprite

1

I want to add a border around my mask. I don’t know if I can add the border directly to the mask or if I need to create something new and position it. I imagine if the border was part of the mask it wouldnt show up? Anyway I added lineStyle to my roomMask and I get this error that doesn’t make any sense to me:

1061: Call to a possibly undefined method lineStyle through a reference with static type flash.display:Sprite.

Is this saying you can’t have a lineStyle on a Sprite? I am not sure what I am doing wrong here.

ActionScript Code:
[LEFT][COLOR=#808080]*//create a mask to cover the room container *[/COLOR]
        [COLOR=#808080]*//to hide the floor outside edges*[/COLOR]
        [COLOR=#000000]**var**[/COLOR] roomMask:Sprite = [COLOR=#000000]**new**[/COLOR] Sprite[COLOR=#000000]([/COLOR][COLOR=#000000])[/COLOR]; 
        roomMask.[COLOR=#0000FF]lineStyle[/COLOR][COLOR=#000000]([/COLOR][COLOR=#000080]6[/COLOR], 0x0000FF, [COLOR=#000080]0[/COLOR].[COLOR=#000080]5[/COLOR][COLOR=#000000])[/COLOR];           
        roomMask.[COLOR=#000080]graphics[/COLOR].[COLOR=#0000FF]beginFill[/COLOR][COLOR=#000000]([/COLOR]0xFF00ff[COLOR=#000000])[/COLOR];
        roomMask.[COLOR=#000080]graphics[/COLOR].[COLOR=#000080]drawRoundRect[/COLOR][COLOR=#000000]([/COLOR][COLOR=#000080]0[/COLOR],[COLOR=#000080]0[/COLOR],[COLOR=#000080]662[/COLOR],[COLOR=#000080]411[/COLOR],[COLOR=#000080]15[/COLOR],[COLOR=#000080]15[/COLOR][COLOR=#000000])[/COLOR];
        roomMask.[COLOR=#000080]graphics[/COLOR].[COLOR=#0000FF]endFill[/COLOR][COLOR=#000000]([/COLOR][COLOR=#000000])[/COLOR];
        addChild[COLOR=#000000]([/COLOR]roomMask[COLOR=#000000])[/COLOR];
        roomMask.[COLOR=#000080]x[/COLOR] = [COLOR=#000080]28[/COLOR];
        roomMask.[COLOR=#000080]y[/COLOR] = [COLOR=#000080]110[/COLOR];
        roomContainer.[COLOR=#000080]mask[/COLOR] = roomMask;

[/LEFT]