Displayiing a "-" for a Zero value where the cell has an existing Indian Currency Format.

Dear Forum,

I use a specific Number format to display Indian Currency using the below mentioned formula in the Format Cells Options:

With Decimal Places
PHP Code: 
=[>9999999]"Rs "#\,##\,##\,##0.00;[>99999]"Rs "#\,##\,##0.00;"Rs "#,##0.00 
Without Decimal Places
PHP Code: 
=[>9999999]"Rs "#\,##\,##\,##0;[>99999]"Rs "#\,##\,##0;"Rs "#,##0 
This gives me a very neat numeric value with the Rs prefixed to the number...
Now I need to get a "-" or just a NEGATIVE MINUS SIGN incase the value is zero for specifically mentioning that the paticular cell has not been filled, I know I can do the same using a regular IF condition but I am not aware whether a Format Cell Option is available which can do the needful..

Warm Regards
e4excel