[quote='lightstriker',index.php?page=Thread&postID= 101809#post101809]Lock1 assist tank target, cast seed
Lock2 assist Lock1 target, tabs to next mob, cast seed
Lock3 assist Lock2 target, tabs to next mob, cast seed[/quote]

I would be careful here -- the "tab to next target" could target something out of range or a pat or a different group and draw in more...

That being said... I'm assuming your tank is either your party leader or your focus...

Lock1:
[quote]/target [target=focustarget,harm,nodead][target=party1target,harm,nodead]
/stopmacro [noharm][dead]
/cast Seed of Corruption[/quote]

Lock2:
[quote]/target [target=Lock1target,harm,nodead][target=focustarget,harm,nodead][target=party1target,harm,nodead]
/targetenemy
/stopmacro [noharm][dead]
/cast Seed of Corruption[/quote]

Lock3:
[quote]/target [target=Lock2target,harm,nodead][target=Lock1target,harm,nodead][target=focustarget,harm,nodead][target=party1target,harm,nodead]
/targetenemy
/stopmacro [noharm][dead]
/cast Seed of Corruption[/quote]


I haven't tested the above, but I'd assume that it works from [url='http://www.wowwiki.com/Making_a_macro#.2Ftargetenemy.2C_.2Ftargetfriend']this page[/url] on /targetenemy macros. You may have issues if there are less than 3 mobs, but I'm not sure about that...