im fairly new to the world of deleting faces

only been using this wonderful feature for 3 or 4 months

ive just started coming across this problem and i cant seem to find a answer

i create my model, use the delete face option 7 or 8 times and finish

come back change a seemingly unrelated feature up-tree from the delete face feature

all of a sudden my delete face feature stops working

apparently i need to "select edges for blending"

see attached pic

how do i select edges for blending? it only lets me select faces?

thanks in advance