yes - you renamed the .dat file of the scenario in question - in this case, #65 - and rename the stock ai file (#1,#2, etc) to the #65 spot you just put on hold.
now a few caveats: you may choose to make some minor edits to bring down the 'rush' to port moresby by the japanese that is, imho, impossible to resist. To do so - go in the editor, to the ai data tab, and look for the scripts that involve port moresby.
specifically -script 047 - change the destination ID to BUNA to have them offload to Buna (or if you want them to invade port moresby then leave it in) and script #218. same thing, remove PM as one of the assualt bases (leaving buna in alone is fine, and the ai might then later move over the kokoda trail and attack overland)
if you dont remove these scripts then it is, imho, impossible to save port moresby unless you get VERY lucky with your early air combat TF's - and i mean, really really really lucky. I tried the first month of the game at least 15 times and i only held moresby 2x.
again, easy to do this, and makes for a great game either way.