Shorthand way of writing repeated formula/links to workbooks in a cell

why not use a cell to store the link and then reference that in the complex formula?

no short hand that I know of.

I'm suggesting that in A1 use have

A1: ='C:\A\[Long_workbook_name.xls]Long_sheetname'!B28

and then you formula would be

=IF(ISERROR(LOOKUP(10^99,--MID("|"&A1,SMALL(IF(((--ISNUMBER(--("0"&MID(SUBSTITUTE(" "&A1," ","|"),ROW($1:$25),1)))=0)*ISNUMBER(--(MID(SUBSTITUTE(" "&A1," ","|"),ROW($2:$26),1)))),ROW($2:$26)),2),ROW($1:$25)))),LOOKUP(10^99,--MID("|"&A1,SMALL(IF(((--ISNUMBER(--("0"&MID(SUBSTITUTE(" "&A1," ","|"),ROW($1:$25),1)))=0)*ISNUMBER(--(MID(SUBSTITUTE(" "&A1," ","|"),ROW($2:$26),1)))),ROW($2:$26)),1),ROW($1:$25))),LOOKUP(10^99,--MID("|"&A1,SMALL(IF(((--ISNUMBER(--("0"&MID(SUBSTITUTE(" "&A1," ","|"),ROW($1:$25),1)))=0)*ISNUMBER(--(MID(SUBSTITUTE(" "&A1," ","|"),ROW($2:$26),1)))),ROW($2:$26)),2),ROW($1:$25))))

No because then you would need to use the INDIRECT functon and that does not would on closed workbooks.
Perhaps an alternative is to use named ranges. Via Name Manager add a named range, for example.

EXT_B28: ='C:\A\[Long_workbook_name.xls]Long_sheetname'!B28

=IF(ISERROR(LOOKUP(10^99,--MID("|"&EXT_B28,SMALL(IF(((--ISNUMBER(--("0"&MID(SUBSTITUTE(" "&EXT_B28," ","|"),ROW($1:$25),1)))=0)*ISNUMBER(--(MID(SUBSTITUTE(" "&EXT_B28," ","|"),ROW($2:$26),1)))),ROW($2:$26)),2),ROW($1:$25)))),LOOKUP(10^99,--MID("|"&EXT_B28,SMALL(IF(((--ISNUMBER(--("0"&MID(SUBSTITUTE(" "&EXT_B28," ","|"),ROW($1:$25),1)))=0)*ISNUMBER(--(MID(SUBSTITUTE(" "&EXT_B28," ","|"),ROW($2:$26),1)))),ROW($2:$26)),1),ROW($1:$25))),LOOKUP(10^99,--MID("|"&EXT_B28,SMALL(IF(((--ISNUMBER(--("0"&MID(SUBSTITUTE(" "&EXT_B28," ","|"),ROW($1:$25),1)))=0)*ISNUMBER(--(MID(SUBSTITUTE(" "&EXT_B28," ","|"),ROW($2:$26),1)))),ROW($2:$26)),2),ROW($1:$25))))

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