try this
addEventHandler ( 'onClientGUIClick', resourceRoot, function( )
if ( source == GUIEditor.button[1]) then
setElementModel(77,localPlayer)
elseif ( source == GUIEditor.button[2]) then
setElementModel(78, localPlayer)
elseif ( source == GUIEditor.button[3]) then
setElementModel(72, localPlayer)
elseif ( source == GUIEditor.button[4]) then
setElementModel(71,localPlayer)
end
end
)