Change List Depending on Cell Entry

I have 2 WS "Estimate" & "Rate Table" sheets1 & 2 accordingly. The rate table has rates in column E. What I would like to achieve is that when a user enters a postcode in "Estimate" C19 this runs a calculation on "Rate Table" Column E depending on the postcode entered (picking up on just the first 2 letters of postcode i.e CT4 5RT

Something Like (in my pigeon code!)

If Sheets"Estimate" LEFT (C19,2)= " inserting many postcodes" then
Sheets "Rate Table" Column E *75%,90%,95%,100%,110%,120%