You can use index only for SEEK starting from the begining of the index expression. To SEEK on the part of the field you would have to create another index

INDEX ON SUBSTR(item, 4,5) TAG item48

>
>i have a table1 with an index 'item', my problem is how seek all items starting in 4th position to the 8th positon without changing my index?
>e.g
>abc14421xyz01
>i need to seek all 1442 using seek statement and not select statement.