Passing paramters to FM - RFC_CALCULATE_TAXES_DOC and RFC_UPDATE_TAXES_DOC

Hi Gurus,

Please guide me on which are the parameters need to be passed to RFC_CALCULATE_TAXES_DOC and RFC_UPDATE_TAXES_DOC.

I tried testing both, but not getting any fruitful results.

I know the Import Parameters are:

I_SAP_CONTROL_DATA, I_TAX_CAL_HEAD_IN, I_TAX_CAL_ITEM_IN

and i get to know results from:

O_EXT_CONTROL_DATA, O_COM_ERR_DOC under Export parameters and

O_TAX_CAL_ITEM_OUT, O_TAX_CAL_JUR_LEVEL_OUT under Tables.

My scenario is something like:

I need to fetch data from BKPF, BSEG, MSEG and pass the relvant data to function module

RFC_CALCULATE_TAXES_DOC to calculate Tax and need to post that tax into SAP as well as external system.

I need to call RFC_CALCULATE_TAXES_DOC twice:

Call 1 - to determine what the tax determination would have been on the original purchase and store the tax amount value.

Call 2 - second time to determine tax on the movement itself (inclusive of cost objects and/or updated locations) and store the tax amount value.

tax amount = call1 - call2.

Now need to update this tax to SAP and External system.