Updates a single named field on a part record for the given `partId`, without needing to supply the full part dictionary. 
Useful for quick, targeted edits � such as flipping a handling flag or correcting a manufacturer part number � from a UI control bound to one column at a time.

---
### Parameters
**partId** `Integer`: Id of part to update<br />
**field** `String`: Valid options are partNumber, partDescription, partCategory, manufacturerId, manufacturerPartNumber, defaultUomId, isCriticalSpare, isRepairable, isSerialized, isConsumable, isActive, notes<br />
**value** `String`: Value to update to<br />
**userId** `Integer`:Id of the user executing the function<br />

---
### Returns
**# of records modified** `Integer`<br />
**message** `String` None if success<br />

---
### Example
```python
# Mark an existing gasket part as a critical spare
partId = 5187
field = 'isCriticalSpare'
value = True
userId = system.kanoa.security.getIDPUserId({'userName': 'SYSTEM'})

recordsModified, message = system.kanoa.inventory.updatePartField(partId, field, value, userId)
print recordsModified, message
```