May not be faster but is is shorter, possibly more convoluted, but I think it does the same thing. If you are trying to determine if the last name is between 2 values ignoring case and last name will be always be followed by space or * or will be only the last name.

*!* Assumes set exact on
RETURN BETWEEN(UPPER(LEFT(insured.po_name,;
        IIF(AT(" ",insured.po_name) > 0,AT(" ",insured.po_name)-1,;
        IIF(AT("*",insured.po_name)> 0,AT("*",insured.po_name)-1,;
        LEN(insured.po_name))))),;
	UPPER(xfrom),UPPER(xto))

>We are searching records for any condition using a from and to condition. Records are stored like so:
>
>SMITH*JAMES
>SMITH III*MICHAEL
>SMITH JR*JOHN
>SMITHERMAN*PETER
>
>I must account for the user entering from: SA to: SMITH or from: SMITH to: SMITH, or from: A to: Z, etc. SMITH to SMITH should NOT include SMITHERMAN...
>
>The below code works (If exact is on and near is off), but can it be faster?
>
>

>xreturn=.T.  && include this record, .f. if record does not meet condition
>  IF !EMPTY(xfrom) OR !EMPTY(xto)
>    IF ALLTRIM(UPPER(xfrom))=ALLTRIM(UPPER(xto))
>      IF ALLTRIM(UPPER(xfrom)) $ LEFT(UPPER(LEFT(STRTRAN(insured.po_name," ","*",1),;
>          AT("*",STRTRAN(insured.po_name," ","*",1))-1)),LEN(ALLTRIM(UPPER(xfrom)))) ;
>          .AND. UPPER(LEFT(STRTRAN(insured.po_name," ","*",1),;
>          AT("*",STRTRAN(insured.po_name," ","*",1))-1));
>          <= UPPER(ALLTRIM(xto))
>        ? po_name+ "    YES a match"
>        xreturn = .T.
>      ELSE	&& not a match
>        ? po_name+"    NO not a match"
>        xreturn = .F.
>      ENDIF
>    ELSE
>      *--TCH 08/13/2003 * for  SMITH III*JAMES, etc
>      *IF !BETWEEN(UPPER(LEFT(insured.po_name,AT("*",insured.po_name)-1)),xfrom,xto)
>      IF !BETWEEN(UPPER(LEFT(STRTRAN(insured.po_name," ","*",1),;
>          AT("*",STRTRAN(insured.po_name," ","*",1))-1)),xfrom,xto)
>        xreturn = .F.
>      ENDIF
>    ENDIF
>  ENDIF
>