I have a custom function wirtten as Custom Assembly which would business
calculation and return a value.

For eg: I have Table with 5 columns, I have to return calculated column (6)
based on the column 3 and 4. To do this we can create custom assembly and
reference in the report (rdl) and write to pass the column 3 and 4 to the
custom function and that would return a value that would be shown on the
report.

That is, I am able to consume this custom function in the report designer/
rdl.

I am not able to do the same in the Report Model, so that I can reference
the custom assembly and then use the shared function to pass the column 3 and
4. The resultant value would a new attribute in the entity.

When I write code in the attribute expression
[code.customassembly.function()]. It says period (.) is invalid.

Hope I am not confusing. Please HELP!..