Nested Computed Dice Roll

Hi!  I'm hoping someone can help me with the syntax on some spell macros I'm working on. 3.5e Wild Mage needs to roll 1d6 to modify the caster level of any spell she casts.  It's actually Caster level -3 + 1d6. So if I cast fireball (normally 1d6 per caster level), it would be (caster level -3 + 1d6)d6.  I can't seem to get the die roller to acknowledge the "d6" on the outside of the parenthesis. Any suggestions?

[[ (caster level -3 + [[1d6]])d6 ]]

Or if you want to ensure that the caster level -3 is a 1 minimum you can use: [[ ([[{@{selected|casterlevel} -3,1}kh1]] + [[1d6]])d6 ]] I've assumed you are using Diana's 3.5 sheet for the attribute name and you can ofcourse drop the selected| if using it as an ability on your sheet.