Check the last value of a string inside the function aggr (Concat (FIELD_A, '',FIELD_B), FIELD_C)

[#1]

Good morning, I have the following problem:

Using the aggr (Concat (DISTINCT FIELD_A, '', FIELD_B), FIELD_C) should check the last field value FIELD_A.
In case there's a number I should put a., and if there was a letter I should not put anything as a separator.

It's possible to define a condition on that?

Thanks

Giovanni Scalzo