Q: How can I replace substring AAA in field value to BBB?
A: Create rule using "find substring" condition and "replace substring" as action.
Use AAA as a condition value and BBB as a replace string.
A: Create rule using "match regular expression" condition and "replace value to" action.
Use (.*)AAA(.*) as a condition value and \1BBB\2 as a replace string.

Q: How to check that column is equal to the sum of another columns, i.e. F3 = F1+F2?
A: Create rule using "compare with value" check. Use '=' as operation and $$(@'F1'+@'F2') expression as value.

Q: How to check that 'Sex' column has 'M' and 'F' values only?
A: Create rule using "in list" check. Use F,M as list. Switch "ignore case" check box is necessary.

Q: How to check that 'HireDate' column less or equal than current date?
A: Create rule using "compare with query result" check and "<=" as operation. Use "select getdate()" as a query.
It is for SQL Server. Please change built-in function name if necessary.

Q: I have Discount column. How to divide in half all discounts greater 0.10?
A: Create rule using "compare with value" check, 0.10 as value and ">" as operation. Use "replace value to" action with "%VALUE%/2" value.