Natur Macro Help

[Strychnos]

I was trying to make a macro so that Natur Enemy Castbar would show my Slice and Dice duration, however I'm not sure if it's possible.

What I have so far is:
/script a = GetComboPoints();
/script a=a*3+6
/cast Slice and Dice
/necb countsec a Slice and Dice

However, it's just not showing anything because I guess it can't identify the 'a' as an integer.

Any ideas?