Create a table with 11 numbers 1.0,1.2,1.21,1.23,1.24 ...... 1.3
Add this table to a query along with the table that has the prices in. DO NOT join the tables
Add the price in one column and in another column add [Price]*[Increase] where Increase is the percentage increase. This will give you a price times the value. Having 1.0 will give you the actual price.