Visible Monster HP Plugin Error

[Snaehild 0]

Can anyone help me with these errors?

1    error C2037: left of 'option' specifies undefined struct/union 'npc_data'    trunkpluginsvisiblemonstershp.c    401    1    VisibleMonstersHP2    error C1903: unable to recover from previous error(s); stopping compilation    trunkpluginsvisiblemonstershp.c    401    1    VisibleMonstersHP3    IntelliSense: pointer to incomplete class type is not allowed    trunkpluginsVisibleMonstersHP.c    401    59    VisibleMonstersHP4    IntelliSense: identifier "FLAG_CLASS" is undefined    trunkpluginsVisibleMonstersHP.c    411    42    VisibleMonstersHP5    IntelliSense: pointer to incomplete class type is not allowed    trunkpluginsVisibleMonstersHP.c    489    59    VisibleMonstersHP6    IntelliSense: identifier "FLAG_CLASS" is undefined    trunkpluginsVisibleMonstersHP.c    499    42    VisibleMonstersHP7    IntelliSense: pointer to incomplete class type is not allowed    trunkpluginsVisibleMonstersHP.c    572    59    VisibleMonstersHP