try THIS:

* sample Call
IF !istagthere("employee","SSN")
INDEX ON ssn TAG ssn
ENDIF


*------------------------*
FUNCTION istagthere
* am checking for 254 tags, not sure if limit is higher now...
PARAMETERS lcfilename,lctagname
IF PARAMETERS() <> 2
MESSAGEBOX("You must pass both Table and Index Name")
RETURN .F.
ENDIF
lncurrarea = SELECT(1)
lbtagexist = .F.
SELECT &lcfilename
FOR ncount = 1 TO 254
IF EMPTY(TAG(ncount))
EXIT && Exit the loop when no more tags are found
ENDIF
IF TAG(ncount) = UPPER(lctagname) && Checks for tags in the index
lbtagexist = .T.
EXIT
ENDIF
ENDFOR
RETURN lbtagexist