Date difference formula issue

Hello,

We have a requirement to calculate no of days using current system date and date coming from an info-object ZOR_DATE( characteristics ) in InfoCube at BEx Level. We have 0CALDAY also in our query. Please tell what can be done to find the number of days subtracting those mentioned days. We need to create a new formula or CKF ? Please tell in detail.

Thanks,

MV