using variable for open workbooks

I am conversant with excel vba

my code statements like this

dim imp1  as workbook, imp2 as workbook,j as integer
set imp1=workbopks("mybook1.xls")
set imp2=workbooks("mybook2.xls")
for j =1 to 2

with workbooks ("imp" &  j)

the last line gives error "subscription out of range"


how to solve the problem(personal.xls file is also open and the above code is parked in that file)