You may wish to configure the Client Code field and/or Cost Code field so that they force users to enter the code in a pre-defined format. You can‘t prevent them from entering an incorrect code, but you can prevent them from recording in an invalid entry that is in the wrong format. Your Client Code and/or Cost Code may be made up of digits and letters in varying combinations. 


Below is a breakdown of the special characters used to create masks:

! (exclamation mark)
If a ! character appears in the mask, leading blanks don't appear in the data. If a ! character is not present, trailing blanks don't appear in the data.

> (greater-than chrevron)
If a > character appears in the mask, all characters that follow are in upper case until the end of the mask or until a < character is encountered.

< (less-than chevron)
If a < character appears in the mask, all characters that follow are in lower case until the end of the mask or until a > character is encountered.

<> (less-than, greater-than chrevrons)
If these two characters appear together in a mask, no case checking is done and the data is formatted with the case the user uses to enter the data.

\ (backslash)
The character that follows a \ character is a literal character. Use this character when you want to allow any of the mask special characters as a literal in the data.

L (upper case L)
The L character requires only an alphabetic character only in this position, i.e. A-Z, a-z.

l (lower case L)
The l character permits only an alphabetic character in this position, but doesn't require it.

A (upper case A)
The A character requires an alphanumeric character only in this position, i.e. A-Z, a-z, 0-9.

a (lower case A)
The a character permits an alphanumeric character in this position, but doesn't require it.

C (upper case C)
The C character requires a character in this position.

c (lower case C)
The c character permits a character in this position, but doesn't require it.

0 (zero)
The 0 character requires a numeric character only in this position.

9 (nine)
The 9 character permits a numeric character in this position, but doesn't require it.

# (octothorp / hash)
The # character permits a numeric character or a plus or minus sign in this position, but doesn't require it.

_ (underscore)
The _ character inserts a blank character in this position. When the user enters characters in the field, the cursor skips the blank character.