How to give string as the input in open office calc extensions

[Samiththa Bashani]

 I tried the example that  is provided in open office tutorials(myRNG:
http://wiki.openoffice.org/wiki/Simple_Calc_Add-in)

As it mentioned it can handled double inputs. But i can't find a way to
handled strings as inputs.
ex:

Sub Main
        mgr = getProcessServiceManager()
        o = mgr.createInstance("org.openoffice.sheet.addin.RNG")
        //MsgBox o.expo(10)   //this is what tutorial has explained.
         MsgBox o.expo("asd123asd")   // this is what i want to read
 End Sub

Detailed answer will be highly apreciated.

thank you.