Actually, you would be better off using a macro for this..
pawn Код:
#define AdminCheck(%0,%1) if(!IsPlayerAdmin((%0)) && pData[(%0)][Level] < (%1))\
return SendClientMessage((%0), ERROR, "Error: {FFFFFF}You do not have permission to use this command!");
Using a stock function, no matter what it returns, it won't really 'break' the code, it will just return a value and continue... macros act as a 'text' replacement.