>thanks Tore for the reply. The are both character fields, the PO number field is 6 characters padded on the left with zeros when the po number is generated

Sergey gave this solution in another thread last year

INDEX ON field1 + CHRTRAN(field2, ;
	"0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz", ;
	"zyxwvutsrqponmlkjihgfedcba`_^]\[ZYXWVUTSRQPONMLKJIHGFEDCBA@?>=<;:9876543210") TAG t1