Unfortunately it's not the same problem. My problem is that I need to use the dimension of the chart as a variable in my chart expression.
FYI, one of my tables has:
Date, HomeTeam, AwayTeam, Result, Full Time Home Goals, Full Time Away Goals, Home Shots, Away Shots etc...
The other table has:
Team, BackgroundRGB, TextRGB, OutlineRGB, PictureLink etc.
The team is in the same format as HomeTeam and AwayTeam - so when team is selected, I have used it as a variable [ "GetFieldSelections($(=Team))" ] to select when Team = HomeTeam, however when Team is used as a dimension in a chart it seems as if it's not actually selecting a Team so this can't be used.