Not working is not very helpful. What is going wrong, specifically? Are you getting an error message (what?) or is one or more of the fields not getting the correct value?
To begin with I don't see a column named "Item Name" in your table and that is what the update query is using to locate the row to update.
Other issues:
1. your code should verify that the record the user is asking to update exists before running the update query.
Beyond that,
1. You need to backup and rethink your table schema. You shouldn't be using this method to update inventory at all. Plus, hard coding warehouses into specific columns is just plain wrong. There is no beating around the bush with this one. Don't do it. If you have to add a new warehouse. You have to modify any forms/reports/queries/code that work with warehouse which is an unnecessary maintenance burden. A warehouse name is a piece of data. Pieces of data are NEVER column names. If you wanted to store the state for a customer record, would you add 50 columns? One for each state? What you have done is to make that exact mistake.
2. You have merged three important functions into a single table.
a. Product list
b. Quantity on hand
c. Inventory movement
You should have at least two tables. One to store the product information and a second to store inventory transactions. To calculate quantity on hand, you sum the inventory transactions for the item/warehouse combination. Take a look at the Northwinds dev sample to see how inventory is properly kept and managed. You will make yourself crazy the way you are doing it because there is no auditibility. By using a transaction table, you get to see ALL movements of inventory, who made them and when so if your cycle count is wrong, you may be able to identify when it happened.
Now, your transfer of stock code needs to create two records. One to subtract the inventory from the from warehouse and a second to add the inventory to the to warehouse. Transfers are aways two record sets. From-To.
3. Using embedded spaces and special characters just makes everything harder to read in the code because all the non-conforming object names MUST be encased in square brackets [] which are jarring to the eye and add two characters to the length of every object name. When you use the object your eyes will play tricks on you and you will see () as [] and vice versa causing coding errors.
There are other issues but start with thinking about these 3.
