Custom Variable Values by Visit Graph (no replies)

Hello
I am trying to generate a graph, which visualizes the number of visits per value of a custom variable by day. This proves to be a lot harder than I expected.
My current request looks like this:

http://stat.server.somewhere/?module=API&method=ImageGraph.get&idSite=3&apiModule=CustomVariables&apiAction=getCustomVariablesValuesFromNameId&language=en&token_auth=[token]&period=month&date=today&idsubtable=[randomNumber]

However this doesn't quite work, thanks to subtables being weird. I can visualize the visits without the variables being into their values by using something like

http://stat.server.somewhere/?module=API&method=ImageGraph.get&idSite=3&apiModule=VisitsSummary&apiAction=get&token_auth=[token]&period=month&date=[datePeriod]&segment=customVariableName1=[variableName]

So I basically want this, but with a line per unique value.

Is there any way to actually get the results I am looking for?
Thanks in advance for your help!