How To Fix GB305 - Expression with & not allowed in matrix validations

GB305 - Overview

• Message type: E = Error

• Message class: GB - Messages used by the Boolean code generator

• Message number: 305

• Message text: Expression with & not allowed in matrix validations

What causes this issue?

You formulated a condition which is to be valuated on every line of the
table. Such conditions are not allowed in matrix validations outside of
a mathematical expression.
Included is this are, for example, expressions with field comparisons
and/or sets. These expressions cannot be processed, since the matrix
validation processes an entire table all at once. These expressions,
however, refer to exactly one line in a table.
Example:
BSEG-HKONT = "400000" not allowed
SUM ( BSEG-DMBTR ) > "100000.00" allowed
Line-by-line field comparisons are only allowed for fields that can
also be used in mathematical expressions. These expressions will be
valuated as true if they are not false for any line in the table.
Examples:
BSEG-DMBTR > "100000.00" allowed
BSEG-DMBTR = BSEG-WRBTR allowed

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

System Response

The expression is recognized as containing an error and is not
accepted.

How to fix this error?

If you want to formulate a condition which is to be valuated per line
in the table, use the application callup point at line level. In FI,
for example, use callup point 0002 (document line).
You also have the possibility of using a user exit in which you can
either partially or entirely code your logical expression using ABAP/4.
You can find more information on user exits in <DS:DE.BOOLEXP>Boolean
sytax</>

Error message extract from SAP system. Copyright SAP SE.

GB305 - Details

• The SAP error message GB305, which states "Expression with & not allowed in matrix validations," typically occurs in the context of SAP Business One when you are trying to create or modify a matrix validation that includes an expression with the ampersand (&) character. This character is often used in expressions to concatenate strings or to reference fields, but its use is restricted in certain contexts, such as matrix validations.
  
  Cause:
  The error arises because the ampersand (&) is not permitted in the expressions used for matrix validations. This restriction is in place to ensure that the validation logic remains clear and unambiguous. The matrix validation feature is designed to enforce rules on the data entered into matrix fields, and the inclusion of the ampersand can lead to confusion or errors in interpretation.
  
  Solution:
  To resolve this error, you should modify the expression used in your matrix validation to eliminate the ampersand. Here are