Hello Alex,
thanks for considering EPPI-Reviewer! I hope you'll enjoy using it.

I think what you are trying to achieve is possible, but it will require some careful planning and pre-processing.
In a nutshell, Excel can export "comma separated files" (.csv); these, if appropriately formatted, can be converted into RIS files via the RIS Export utility. Thus, rearranging a copy of your excel file might be enough to allow importing your references into EPPI-Reviewer.
However, doing this for the whole file in one go will not distinguish between included, excluded and not screened references, so it won't be good enough and more pre-processing will be needed.
In particular, you'll need to export your references in groups, defined by their current screening status, at minimum I guess this means 3 batches: all includes, all excludes and the remaining references. If you've recorded the reasons for exclusion, you may want to export the excluded records in smaller batches, one for each reason.

You would then pass all the exported CSV files through the RIS export utility and import the results in EPPI-Reviewer. At this point you'll need a suitable screening codeset (able to represent the decision you've already made), and will then bulk assign the appropriate items to the corresponding code (Included, excluded because X, etc.) based on their "source" batch. This last bit is quite easy and well documented, while  exporting to the correct kind of CSV isn't (it's quite new!).

We can offer in-detail guidance for the whole procedure, but would need to receive an example of your excel data to start with. Can I ask you to send your excel file (or just a few "example rows", if you prefer) via email? You can reach us at EPPISupport@ucl.ac.uk.

Thanks and best wishes,
Sergio