I need help with a formula that will be able to lookup a part name and when
it finds it a worksheet it can sum the weekly values to return the monthly
total.

data table:
Part Wk 1 Wk 2 Wk 3 Wk 4
pen 10 20 30 40
clip 20 30 40 50

Formula needs to vlookup Pen and return the sum of wks 1-4 = 100. Was
researching SUMPRODUCT but not sure if that's the solution and unclear on how
to apply it. I am hoping for a formula that is an array instead of needing
to add multiple vlookups together. Also if anyone has a good link to explain
SUMPRODUCT I would appreciate it. Thanks in advance.