LOVAL /HIVAL in SQL

I came across the trick of using the BETWEEN OPCODE in embedded SQL statements and it looks like a great way to handle multiple variable select statements. However, I can't get it to work, even with interactive SQL. The interactive SQL looks like this:

select * from myfile where myfield between '*LOVAL' and '*HIVAL'

myfield is a character field. If I don't use the single quotes, I get a runtime error "Token * was not valid." If I do use the quotes it runs but I get no output.

In my RPG I have (snippets):

D q S 2A Varying
D Inz('''')
/free
if actcode<> *blanks;
act1 = q + actcode + q;
act2 = q + actcode + q;
else;
act1 = '*LOVAL';
act2 = '*HIVAL';
ENDIF;

exec sql
select * from myfile where myfield between act1 and act2;


That statement, with *LOVAL/*HIVAL should return me all the records, but it returns nothing. What is the proper syntax? What have I missed?

Pete Helgren