[Vedran]

Would this work?

IF
Level(Valygar,15) //If Valygar is level 15
HasItem(NPSW04,Valygar) //and he has his blade in inventory
THEN
RESPONSE #100
TakeItemReplace(NPSW04,NPSW04A,Valygar) //then take it and replace it with better blade
END

IF
Level(Valygar,20)
HasItem(NPSW04A,Valygar)
THEN
RESPONSE #100
TakeItemReplace(NPSW04A,NPSW04B,Valygar)
END

IF
Level(Valygar,25)
HasItem(NPSW04B,Valygar)
THEN
RESPONSE #100
TakeItemReplace(NPSW04B,NPSW04C,Valygar)
END

...