It is a good development practice to provide value help on selection screen. In contrast with date field month does not come with standard value help. Instead of coding month value help in each report I recommend defining generic one in common include and reuse wherever needed.
Using of Z_MONTH_F4 generic value help is very simple.

Lets generic month value help in action






Source code can be downloaded here:
Z_MONTH_F4_DEMO
Z_MONTH_F4_DEMO_TOP
Z_MONTH_F4_DEMO_APPL
Z_MONTH_F4
Using of Z_MONTH_F4 generic value help is very simple.

Lets generic month value help in action






Source code can be downloaded here:
Z_MONTH_F4_DEMO
Z_MONTH_F4_DEMO_TOP
Z_MONTH_F4_DEMO_APPL
Z_MONTH_F4