I have thi sheet and 2 column

AAAAA 123456
AAAAA 128456
AAAAA 123457
BBBBB 123456
BBBBB 128863
BBBBB 129226
CCCCC 234556

i need to loop all cells into sheet and fill a dictionary in this mode:

AAAAA not exists add, AAAAA and related value 123456

AAAAA just exists, add 128456 to the already exists combination

ecc


to the and of cell loop the dictionary filled