Hi
A couple of ideas:
Only bet if the last matched back bet was made less than 4 hours ago:
selections trigger expression (now_time-bm_backtime)/mf_hour is less than 4
or record the scores with a timestamp and only bet if the scores have changed in the last hour, otherwise delete market:
TRIGGER
record market_score1 score in user variables score_var1 and score_var2
record now_time in time_var
repeat this trigger every 10 mins or so.
BETTING TRIGGER
checks market_score1 is not equal to score_var1
or checks market_score2 is not equal to score_var2
and (now_time-time_var)/mf_hour is less than 1
TRIGGER
Delete market
checks market_score1 is equal to score_var1
and checks market_score2 is equal to score_var2
and (now_time-time_var)/mf_hour is greater than 1
A quick check on the Betfair API-NG rollout shows a Tennis Scores and events API is due for release 16th June. It might incorporate info like this.