That errors means the first parameter's type for that database hasn't been defined anywhere.

Here's an example of the first parameter's type not being defined (and the value isn't defined either):
Code
PROC
MyMod_AddEnemy((CHARACTERGUID)_Enemy)
THEN
DB_MonkWorks_SpawnedEnemies(_Level, _Enemy);

Here you can see the type for _Enemy is defined, while _Level is an unknown value and type.

This:
Code
PROC
MyMod_AddEnemy(((STRING)_Level, (CHARACTERGUID)_Enemy)
THEN
DB_MonkWorks_SpawnedEnemies(_Level, _Enemy);

Or this:
Code
PROC
MyMod_AddEnemy((CHARACTERGUID)_Enemy)
THEN
DB_MonkWorks_SpawnedEnemies("None", _Enemy);// "None" is a STRING

Will compile correctly.

LaughingLeader's DOS2 Mods