How can i get a value from a Web Addin

Hello ,

i have some problems to get a value from a Web Addin.
So my Interface function is:

[ApplicationVisible]
string GetValue(ref string strReturn);

The funkttion is JS (TS)is:

function GetValue(strReturn: string): string {
strReturn = 'Ref return text ..A500';
return 'Simple return';
}

The call in C/AL lock like this:

test1:= CurrPage.WebCtrl.GetValue(test2);


Both C/AL variables test1 and test2 are empty. If i call the funtion in any browser the returns are well.
I know, i can trigger any calls from JS via Microsoft.Dynamics.NAV.InvokeExtensibilityMethod. But this is not my solution.

thx in advance
hoffi