Inventory Price Update

Exported inventory list from QuickBooks to Excel. Converted vendor price list from PDF to Excel. Imported both as sheets into a new workbook, where I started formulas to say IF a vendor's part number for an item in the QuickBooks sheet matches a part number in the vendor list, copy the vendor's new price to a new column next to the old price. Then have a column which calculates the percentage change from the old vendor price to the new vendor price for each item found. Kinda got one column working, except it doesn't look for BLANK SPACES, so the outputted column data is about 50% blanks.