As far as I am aware you can just tag @mouseover on the front of your ones ( in the square brackets that is ) and if you wanted to, harm/help depending on if they are for allies or enemies.
For example:
/cast [@mouseover,help,combat,nodead] Blessing of Protection
Should, in theory, check for a living ally in combat when you mouseover and then when you press the keybind, it casts the spell.
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