Modify Expression

[upaliwije]

sum({<R_YEAR=, R_MONTH={'>$(=max(R_MONTH))'}, To_YEAR={$(=max(R_YEAR)+1)},To_MONTH={'>=$(=max(R_MONTH))<=$(=max(R_MONTH))'}, POL_TYPE={'F'}>}[PREMIUM] )

Pls refer my attachment and I want the above highlighted part of the expression to change as R_Month should be months coming after the R_Month and all other conditions should remain as it is

Eg If User select R_Month=Jan Expression should select Feb-dec

                         R_Month=Dec Expression should select Jan-Nov etc

                          R_Month=Jun Expression should select Jul-May etc

Pls help me