How can I define outline of icon on a diagram in Calc?

[geocsaba]

Hi!
Is there a way to define outline of Data series’ icon on a graph in Calc? Without black outline the icons merged and it looks embrassing.
In Excel there in a option to define the line style and the line width of outline of icons. In Libreoffice only color and shape of icons can be modified when I click double on Data series.

I use LibreOffice 4.2.8.2 on Ubuntu.

Thanks.