<script type="text/javascript">myChart.setDataXML("<graph caption='Increase font of caption here'> ...
<script type="text/javascript">
Thanks!
Could you try using <styles> to define your own font specifications and apply it to caption object?
<styles><definition><style name='myFont1' type='font' size='15' color='ff0000' /></definiton><application><apply toObject='CAPTION' styles='mYFont1'/></application></styles>Note that thre are lots of other font attributes to set.