you need to use an output style where the directions are to “not sort” citations to maintain the order of your input. (this may or may not cause problems in other groups of citations). (I think Harvard is set up with this setting).
I used some citations from my own library to create the following version. – apart from a comma before some “and” clauses, I think this reflects your needs?
(see Bartram et al., 1987, Allan and Shepherd, 1987, and Hagemeijer, 1987 for introductions to ‘phase’ models, and La Rosee and Deininger, 2010 for an empirical test of their descriptive and prescriptive validities)
in the unformated (temporary) citation group, it would look like this.
{see \Bartram, 1987 #16;Allan, 1987 #6;and \Hagemeijer, 1987 #80 for introductions to ‘phase’ models;and \La Rosee, 2010 #6946 for an empirical test of their descriptive and prescriptive validities}
In the following using the edit citation (right click edit citation, more) you need to associate the following text with the square bracketed items in prefix/suffix for that citation including spaces as needed. (the square brackets are illustrative only, the above is what appears if you convert to unformatted citations, and I find it easier to add additional text in this form, with the \ following the prefix for an individual citation, rather than use the edit citation tool which you need to save and reopen to add text to the next citation.)
{[Bartram, 1987 #16];Allan, 1987 #6;[and \Hagemeijer, 1987 #80 for introductions to ‘phase’ models];[and \La Rosee, 2010 #6946 for an empirical test of their descriptive and prescriptive validities]}
I added a screen shot of the edit citation dialogue for the above group)