Is it possible to link from one workbook to another workbook using a
dropdown?

I have source.xls
Defined Name: Numbers
refers to: =Sheet1!$A$1:$A$30

when I try to set up my Data Validation for my dropdown in my
destination.xls
I get the follwoing error
"You may not use references to other worksheets or workbooks for Data
Validation criteria"

Am I trying to do the impossible?

Any help is much appreciated