Try something like this:
<plugin clsid="{0BA8ABB8-1F1D-417f-88C6-DA8530E2E7A6}" name="missedcalls" height="14">
<background>
<format state="unselected" x="91" y="18" w="80" halign="left" bgcolor="transparent" fgcolor="#FFFFFF" font-weight="normal" font-size="11.4"/>
<format state="selected" x="91" y="18" w="80" halign="left" bgcolor="transparent" fgcolor="#FFFFFF" font-weight="bold" font-size="11.4" />
</background>
<label> <text>Missed calls: <calls /></text> </label>
</plugin>
I don't think this plug-in takes the b-border-width parameter.