Your best bet would be to use a column of helper formulas:
=NOT(ISERROR(MATCH(A1,'[Linkedbook.xls]Sheet1'!$A$1:$A$50,False)))

and use those formulas returning TRUE as the basis of the formatting: in the Formula is, use =B1
(replace B1 with the first cell with the formula above).

HTH,
Bernie
MS Excel MVP


"gootroots" wrote in message
...
I am looking to highlight duplicates in one workbook based on values from
another workbook

testbook! sheet1 A1:A10
values contain text string

linkedbook! sheet1 A1:A50
values contain text string

any duplicates in linkedbook! will be hightlighted in testbook!

I know how to use conditional formatting but need a little guidance when
linking to another workbook.

thank you in advance of any help