passing function result as variable

[Seven7]

this works : 

='[Table.field]={"*"}'

why this can't work ?

='Left([Table.field])={"A"}'

i'm paasing this variable to COUNT function 

[GaryGiles · Accepted solution]

You can't use a function for the left argument in a set analysis criteria.  Maybe try this instead:

='[Table.field]={"A*"}'