how to run an sql from a subroutine in a subform

I'm trying to run an sql update query (in VBA) to update values in a table, from calculated field values in a subform (using a query as a record source).

Is this possible , and if so, can I call the subroutine from the parent form, and

what would be the correct syntax for the VBA sql string (i'm guessing it would be a docmd.runSQL sqlstringname )??

Any suggestions welcome...

how to run an sql from a subroutine in a subform