From the information you give, I guess that you are using the Keil C51 compiler - but you really do need to make such details clear in your question.

As Andy has pointed out, all the information you need is in the manual.

    mov DPTR,?functioname?BYTE 

Will not work as you can only load the DPTR with an immediate value. For example:

    mov DPTR,#?functioname?BYTE 

However, this almost certainly is not what you need because C51 passes most parameters in registers.

Please confirm the compiler and post your function declaration.

Meanwhile, you will find some examples here:

http://www.programmersheaven.com/search/li...7%2Ehtm%3F

Although I don't think any of these examples includes a pointer to a structure.