How to get data from a char array to a string variable?

Hi Experts,
I'm using Delphi 7.

How do I get character data in an array to a string?  I'm using a For loop because I only want a subset of the data from the array.
The code below does not


Thanks much!

var
  Buffer : array [0..MAXFILESIZE] of char;
  OCRString : string;
 
for i := posBegin to posEnd do
    OCRString := OCRString + (Str[I]) ;
 
My string looks like this:
ABCD#/ABC|DEF|GHIJK\#l;f-3 094QWERalsefd
            
I want to extract pos 4 to 19 (start with first # and end with K before the \).
 
The output OCRString in debug mode looks like this: #0#$12#0#0#0#1#0#0#0#1#0#0#0'4'#0#0#0

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