You mean to say there is a WS-STRING with length of X(10) and you are checking every character from "A" to "Z" and move WS-String to some variable, if condition is satisfied. So in total 26x10 = 260 comparison. Is that the understanding ?
Another thing, if it is a char field, checking for first position itself would take you out of Evaluate check. As it would contain some value between "A" & "Z" then why to code check for other 9 positions. So it'll help, if you can describe more on what is actually you want to check this field in such a way.
You can use the below code.
01 VAR1 PIC X(20) VALUE 'AB485#$%CD'. <- Assumed i/p string
01 VAR1-LEN PIC 9(2).
INSPECT VAR1 TALLYING VAR1-LEN FOR CHARACTERS BEFORE INITIAL SPACE.
J = 1.
PERFORM VARYING I FROM 1 BY 1 UNTIL I > VAR1-LEN
IF VAR1(I:1) >= 'A' AND VAR1(I:1) <= 'Z' THEN
MOVE VAR1(I:1) TO VAR2(J:1)
COMPUTE J = J + 1
DISPLAY 'VAR2 = ' VAR2.