sql update via a combo box

i wish to update a table which has numerous fields but i only want to update one field within the table.
i wish to update all the records in one particular field of the table to the value displayed in a combo box
Does anyone know the SQL required to make this happen?

thanks

The update will change all the records to the same value, or each record has the different value in the combo box?

the update will change all the records to the same value (the value that is displayed in the combo box)
thanks don

UPDATE table_name SET table_name.col_name = comb.value;