FB1.5

I would like to know how to return the text contents of a BLOB field
from a stored procedure.

I am trying the following, which gives an error "conversion error from
string" error # 335544334:

declare variable CustMemo VarChar(2048);
...
Select MEMO_CUST from ORDERS where INVOICENUM = :INVOICENUM
into :CustMemo;

thanks,

Rick