Once you enter an amount for Nominee dividends, all the items are pro-rated automatically.

IE, $100 box 1, $50 box 2, $1,000 box 3, $77 box 2b. You want to show 50%.

Add box 1 and box 3. This is the total dividends, $1,100. Boxes 2 and 2b amounts are already included in boxes 2 and 3. Enter $550 as Nominee amount.

Sch B is $50, Sch D is $500, Qual Divs is $25, Sec 1250 gain is $38.