Setting Default Values In Combo Box To Match The Value Of Previous Record

G'day. I've been browsing the forum trying to find a solution to a problem, without much luck, and am hoping that someone might be kind enough to help me more directly.

I'm a biologist and a newbie to access: with the distinction of being completely clueless about VBA. Nonetheless, I have been tasked with creating a database for storing data obtained from biological surveys of juvenile salmon and harvest/spawner surveys of adult salmon.

The bones of the db are in place and functional. The problem I have is streamlining the data entry process to minimise keystrokes/mouse clicks.

I have a subform for entering fish records with attributes such as 'species_name', 'fork_length', 'count', 'presence of tags, etc. The idea is that fish can be entered as individuals (count=1) or groups (count>1) with attribute data at the appropriate level (eg, fork lengths only entered for individuals. We typically measure the fork lengths of the first 20 individuals of each species and then tally the remainder).

One problem I face is that fish often occur in schools, and it becomes quite tiresome to click and select the same species_name combo box value for each record when entering multiple individuals of fish of the same species.

What I would like to do is set the default value for that combo box (on the fish subform) to match the value entered for the previous record.

I suspect that you could use the after update trigger to execute some code to change the default value each time something is entered manually into the combo box. Unfortunately, I know nothing about how to write the appropriate code.

Can anyone offer me some guidance?

Thanks in anticipation.
Sincerely,
Craig Dolphin