Well, there MIGHT be a way to do this. It depends on the reliability of that input format ALWAYS being LastName, FirstName. A few possibilities come to mind.
It is possible to build a function in VBA to do this sort of rearrangement. Or you can try to build a complex expression in one of your queries.
This function or complex expression can be used as a pre-processing step when you are importing but before you do your search. Perhaps something like, import your data from spreadsheet to temporary table, then run a MAKETABLE query to build the REAL data, using the complex expression in the MAKETABLE rather than the search query. MAKETABLE queries are linear. A search query might take longer with a complex expression in the midst of trying to match up names.
If you are not familiar with these functions and the concatenation operator, then read up on them. They work either in VBA or in the query design grid (and therefore SQL).
InStr, Len, Left, Right as functions and & as an operator.
OK, here is what you would do. Assume the input field name (with comma) is stIName for the snippet below and stOName is the re-ordered name. This is the VBA, with hard RETURN forced in to separate the components.
stOName =
Trim( Right( stIName, Len(stIName)-InStr(1,stIName,",")))
& " " &
Trim(Left( stIName, InStr(1,stIName,",")-1))
Now, if you want this in a query grid, drop the "stOName="
NOTE: This won't work correctly for any name that isn't in the format "LastName, FirstName" - so it would be a good idea to sanity check everything. Which is why I mentioned a VBA function. If you know how to write a public VBA function in a general module, you can use that function in queries, forms, etc.