I can't open your DB at the moment, don't have 2007 on this computer.... But, First thing I see is your table structure.
WHEELS (ID, PN, SN, OH_CYCLE)
OH_CONTROL (ID, PN, OH_CYCLE, ACTION, CONDITION)
First, I would not use spaces....they get you into trouble.
tblWheels (WheelsID, PN, SN...