Sum value in a third column if columns 1 and 2 contain same value

Hey there,

I need help with a Sumifs and/or vlookup formula.

Was wondering how to sum a corresponding 3rd column value if 2 other columns contain the same values, but not on the same row for instance.

Col A ... Col F ... Col H
123456 777777 21
000000 888888 82
777777 444444 99
989898 787878 101
787878 222222 72


My formula would at this point spit out 122.. which is 21+101 because 787878 and 777777 are the only 2 matching cells and 21 and 101 are beside the match that is in column f.

To make this more complicated they aren't beside each other and I am linking the formula to another sheet.

Thanks

Travis

sorry for the lack of excel file but I believe I explained my problem, thanks