magento 1.9 - Shopping cart rules need to apply to original price only, excluding all tier price discounts -

is there way or extension exclude tier pricing discounts when shopping cart discounts applied?

basically want avoid customer receiving both discounts.

i shopping cart discounts apply original price.

for example;

original rice $35 - 20% = $7.00 discount ($28.00 per unit)

multi-buy 2 units changes original price $33.60

$33.60 -20% = $6.72 discount (1 unit @ $26.88 + 1 unit @ $33.60) = $60.48

the main problem face if user selects different flavours.

here user receives tier discount 16% , further 20% on each unit.

i can't afford loosing money when happens.

$29.40 - 20% = $5.88 = $23.52 per unit

therefore if shopping cart discount on rides tier discount , applied original price $35 not problem. customer pay $28.00 minimum units , flavours.

in conclusion; shopping cart rules need apply original price only, excluding tier price discounts.

please suggest me idea.