report - replacement path --calculation of diff b/n dates

Hi gurus,

I'm developing a global recievables ageing report

my issue is in order to calculate the difference of days i had created 2 formula replacement path variables

one using the customer exit -i'm picking the sy-datum here and the other formula variable created on due date.

Now my issue is i'm getting the result for var1(sy-datum) - var2(due date) = X.

customer exit i had use for picking the sy-datum

WHEN ZFCURDATE

CLEAR L_S_RANGE.

L_S_RANGE-LOW = SY-DATUM.

L_S_RANGE-SIGN = 'I'.

L_S_RANGE-OPT = 'EQ'.

APPEND L_S_RANGE TO E_T_RANGE.

please throw some light on this.

I had searched forum i could not find the correct answer for this.