Hi Mohammad,
See below screen shot, I have tested the same case which you have tell me.
In Pricing Procedure, as Mentioned in Second screenshot,
In Sequence, ZCHB should be first, then PR00.
System, checks Base Price in sequence as shown First Screenshot.
By this setting, If PR00 will be present, ZCHB will be in active, even though use has updated it by mistake manually.
If PR00 is not available, ZCHB will be active.
Regards,
MJ.