!if("slot 9" and character is not "slot 9" and character in "Paladins Holy")/castsequence reset=10,combat Blessing of Kings, !Seal of Insight
!if("slot 10" and character is not "slot 10" and character in "Paladins Holy")/castsequence reset=10,combat Blessing of Might, !Seal of Insight


Of course, this did not work. After re-reading the manual, I misunderstand what "slot #" does (it just checks so see if a character is present in that slot).
Come on now this is somewhat simple logic and it's almost in plain English.

The reason you are confused, is because you're apparently using the Universal Invite Macro as an example, which uses this logic to make sure your character does not try to invite a) an empty slot (thus the if "slot 9" part) or b) himself (thus, the if character is not "slot 9" part), and then proceeds to /invite {SLOT9} -- or rather 1 through 5, but in your example we're talking about slot 9 so just follow along..

The second clause of the !if you're looking at is "and character is not "slot 9"" If you take out the "not", then you will instead have ... "and character is "slot 9"". This is all you need.

The logic you intended:
Code:
!if (character is "slot 9" and character in "Paladins Holy") /castsequence reset=10,combat Blessing of Kings, !Seal of Insight
!if (character is "slot 10" and character in "Paladins Holy") /castsequence reset=10,combat Blessing of Might, !Seal of Insight