Chart from relative time dimensions

[aliclowes]

HI

In reportstudio 8.3 I was able to build a chart with 2 series, which showed 3 years information at year level and 24 months information at month level on the x axis.  This showed as 27 separate bars, the 3 years data one colour and the 24 months in a different.  However when I migrated to 8.4 I now find the 3 years data is shown at year and month levels similarly with the 24 month data so I end up with 27 bars in the 2 colours.  I have raised a call with Cognos but they say this is how 8.4 works.  I am building this chart from a cube and wondered if I could use the override dimension option in the query to make the 24 months and 3 years into 2 separate dimensions.

Has anyone come across this before, if you show the same information as a crosstab you do not have the same issue it only appears to happen with a chart.

Thanks in advance

Alison