21. In a system for processing commands entered by a user, the commands including expressions which resolve to a result, a method comprising: (a) receiving input from the user specifying a desired expression; (b) dividing said input into a plurality of tokens, said plurality of tokens including at least one operator token and at least one operand token; (c) determining validity of said desired expression by comparing said tokens against a set of rules specifying valid relationships between tokens; (d) if said desired expression being created is determined not to be valid in step (c), automatically modifying said desired expression so that validity of said desired expression is maintained; (e) placing at least one proxy token for a token whose absence from said desired expression would render said desired expression invalid or incomplete; and (f) using said desired expression in resolving said result.
21. In a system for processing commands entered by a user, the commands including expressions which resolve to a result, a method comprising: (a) receiving input from the user specifying a desired expression; (b) dividing said input into a plurality of tokens, said plurality of tokens including at least one operator token and at least one operand token; (c) determining validity of said desired expression by comparing said tokens against a set of rules specifying valid relationships between tokens; (d) if said desired expression being created is determined not to be valid in step (c), automatically modifying said desired expression so that validity of said desired expression is maintained; (e) placing at least one proxy token for a token whose absence from said desired expression would render said desired expression invalid or incomplete; and (f) using said desired expression in resolving said result. 23. The method of claim 21, wherein each said at least one proxy token is color-coded for representing a required data type.