How to use string interpolation in JsReport correctly?

Question

I need to call a function within another function but my inner function is not calling. So, just want to know if I am doing it syntactically incorrectly.

{{localizeExt
    "jsreport.footer.paging-numbers.prefix"
    "./DeclarationForm/translations"
    startPage=\[\*\*getPageNumber \*\*@index\] endPage=\[\*\*getTotalPages \*\*@root.$pdf.pages\]
}}

localizeExt is the function that takes 3 parameters.

1. The first parameter is "jsreport.footer.paging-numbers.prefix".
2. The second parameter is "./DeclarationForm/translations".
3. The third parameters are getPageNumber and getTotalPages and these are inner functions.

I tried with the return function and all the syntax but none of them are working.