Creating Net Change and New Records to insert/update

[agcrump]

I am looking for a way to compare two tables. If the rows are the same, ie all columns match, then I want to throw that record away. If all the columns are the same except for 1 numeric column, then I want to update the record with the difference of the numeric column. If any of the other columns are different then I want to insert that row.

TBL1
Col1 Col2 Col3
A B 10
C D 5

TBL2
Col1 Col2 Col3
A B 30
C D 5
E F 17

Resulting TBL3
Col1 Col2 Col3
A B 20
E F 17