Hello Surya,
In EPM, you can create local member whose formula can be derived from other cell by selecting Use Excel Cell Reference and in Formula box giving the reference of same.
With respect to Related to Context, you can give local member formula based on combination of context.
For example: In below local member formula I have added the value of 2013.11 & 2013.12 context (i.e Both the context are of year 2013). If don't select the Related to Context then after changing the context to 2014, local member formula will disappear. If I select the Related to context then after changing the context to 2014, it will add up the value of 2014.11 & 2014.12.
Hope this helps..
Regards
Bhagyesh Ravange