Follow these steps to nest function with SUMIF

Click the cell in which you want to enter the formula.

To start the formula with the function, click Insert Function Button image on the formula bar Button image .

Excel inserts the equal sign (=) for you.

In the Or select a category box, select All.

If you are familiar with the function categories, you can also select a category.

If you're not sure which function to use, you can type a question that describes what you want to do in the Search for a function box (for example, "add numbers" returns the SUM function).

To enter another function as an argument, enter the function in the argument box that you want.

The parts of the formula displayed in the Function Arguments dialog box reflect the function that you selected in the previous step.

If you clicked IF, the Function arguments dialog box displays the arguments for the IF function. To nest another function, you can enter it into the argument box. For example, you could enter SUM(G2:G5) in the Value_if_true box of the IF function.

Enter any additional arguments that are needed to complete your formula.

Instead of typing cell references, you can also select the cells that you want to reference. Click Button image to minimize the dialog box, select the cells you want to reference, and then click Button image to expand the dialog box again.

I hope this helps!
Tim Paine