Hi Swetha,
I believe you are selecting Time members in Edit Report. Since your report does not have fixed column structure (since you dont want all member combinations), you would have to manually refer the Time members in EPM Olap formula for Time. Hence whereever EPM Olap Members for Time are populated, just refer the 1st argument of formula to an excel cell and in that excel cell just enter the time member you want to pop. Repeat this for all time members.
Let me know if you face any issue.
Regards,
Raman.