there's LOTS of ways of doing this!
the question is, how do YOU want to do it.
How are you entering the SKU number?
What are you doing with the results?
Why not use a button on the sheet to open
an input box for the user  to enter the SKU.
Then, pass this SKU to your function.
Have your function  do the VLookup
(you can use Application.Worksheetfunction.VLookup
or code a search loop to look it up)
then use this info for your existing function.
When you're done, you can put the results in
the cells of the sheet.
Or... you can create a Change Event for the sheet
that fires off the function that would read
the SKU and supplier from the sheet.
If you need help (or more info) with either approach,
let me know...