Forgive me if this has been asked before as I could not find the answer via search.

I'm planning to do a trip to CPH and ARN.
Currently there is a sale fare for ex-SIN but with limited seats for ARN.

I'm planning to do an open jaw, but the online system does not allow me to easily search flexible dates. I managed to successfully get an open jaw ticket at the sale price by searching for SIN-CPH rtn and SIN-ARN rtn and then using those dates for the open jaw.

However this method only gives me the dates that have inbound and return flights at the sale fare. Hence I'm guessing there should be more dates where I can do a SIN-ARN // CPH - SIN at the sale fare - as there could be days where the outbound is on sale and the inbound is not

It's a bit hard to explain it in words, but basically I want to find all possible dates that I can do this open jaw itinerary efficiently.

Thanks in advance for the help!