I'm thinking that since you're not familiar with VBA (and even if you were a little), creating and coding a userform on which to enter data might be an inconvenient way to go. Rather, we could just put code behind the worksheet that would aid in your data entry. I'm assuming that you could create a lookup table on another sheet that would list all the possible Items in column A, and their Category in column B, that could be used in a lookup table. Then maybe have the data entry/code process work something like this:

1. Enter Product in A2
2. Enter Doc # in B2
3. Enter Item in C2
4. Code looks up Category and puts it in D2
5. Code calculates Formula and puts it in E2
6. Code copies values from A2, B2, and E2 to A3, B3, and C3 as default values for the next row, and selects cell A3
7a. If the default values are correct, user tabs to C3 and enters Item. Code continues as in step 4
7b. If a not, enter the new Product in A3. Code clears B3:E3. User continues as in step 2

What do you think?