Restrict alpha/string field

[Alpha]

Please, I have an alpha field field that has a length of 15, i would like to restrict the characters that one can enter into
the field. Example address of the household for all clusters will contain the following characters " G,F,D,/ , 1,2,3,4,5,6,7,8,9,0".

Interviewers should be restricted to this characters. I tried the poschar function but i was not able to achieve the restriction.

Thanks in advance

[josh]

You can loop through the characters in the field and check each character to see if it is one of the allowed characters. Something like:

PROC MYALPHA

string validChars =  "GFD/1234567890";

// loop through characters in string one by one from first character
// to last non-blank character
do numeric i = 1 while i <= length(strip(MYALPHA))

    // Get character at position i
    string char = MYALPHA[i:1];

   // Check if this character is valid by checking its position in the string of valid characters.
   // A position of zero means it is not in the string so it is invalid.
    if pos(char, validChars) = 0 then
        errmsg("Invalid character '%s'. Only the following characters are allowed: %s", char, validChars);
        reenter;
   endif;
enddo;

[Anysia]

Thanks Josh, it works perfect.

[pcpak]

Hi Josh,
Can this be done on numeric field?
Suppose I have a numeric field of 5 digits and I want to populate a message when user enter less than 5 digits.
thanks

[Gregory Martin]

For a numeric field, you could add a value set to the field, allowing codes 10000-99999. Or you could write:

PROC VALUE

    if VALUE < 10000 then
        errmsg("...");
        reenter;
    endif;