I need a way of searching the columns and highlighting the row(s) which contain the same values in column A & B.
See if Conditional Formatting helps you in this case. Highlight your range in column A, then click on Format > Conditional Formatting, under Condition 1 choose Formula is, and in the field to the right of that enter =A2=B2. Click the Format button, Patterns tab, and choose your highlight color. Click OK, then OK again.
Highlight the corresponding range in column B, and follow the same steps, but this time enter the formula =B2=A2.
These formulas assume your columns' data starts in row 2, and that you highlight the columns' data beginning with row 2.