Table function

By which I mean a function that can be called from any field/column in that Table.

I have a function to update a couple of fields based on the values of 2 other fields and really need to call that function when updating either of those 2 latter fields. I could just put the same code into the 'update' formula for both of those fields, but it's never a good idea to have to duplicate code.

I tried to create a Global function, but it doesn't know about the columns in the table with which I am working and trying to work around that requires a lot of messing around copying values back and forth between parameters and the actual fields.

I thought about adding the function to either the Table create or update formulas, but I cannot seem to then call the function from the fields that need to trigger them.

So, is there any way to create a 'Table function' that can be accessed from any field in that Table, in a similar way that 'Global functions' can be accessed globally?