If you want get back a result you need to pass a pointer to an Extended numeric variable or a pointer to a dynamic string.
In PowerBasic you would need something like:
[code=vb]'---To get back a numeric:
DIM MyExt AS EXT
thinBasic_FunctionSimpleCall(sBSTR, VARPTR(MyExt), %NULL)
'---To get back a string:
DIM MyString AS STRING
thinBasic_FunctionSimpleCall(sBSTR, %NULL, VARPTR(MyString))[/code]
If you are in FreeBasic, I think it is something similar.