Create wordpress calculation plugin (widget in sidebar)

I need wordpress plugin (widget in sidebar). It should be a calcultation form (see attached png): 1. Dropdown "City" - one of six cities - no need to add more. 2. Date1 from (year and month, without day, from 1994-01) 3. Date2 to (year and month, without day till last month added in admin panel) And after all 3 options would be selected, below these inputs would appear (no button) percentage change of City index (from date1 to date2 ). I'll send you excel with these indexes. Percentage should be with one digital after comma (1,1%) and rounded like in excel - (1,15 = 1,2). If percentage change is negative - red color, positive - green. It should be ability to add new data (6 numbers for every city) every month in admin panel. And it is imporant to add indexes with accurate numbers - 6 numbers after comma.