Google Sheets: Using user input data in a single cell to subtract information in other cells

[p_s]

Hi,

I've been scouring through a lot of tutorial videos but that's just leaving me more confused on how to proceed. I know what I want to do, but I don't know what function/formulas I need to achieve my solution, could you help me out by guiding me to the correct formulae?

My sheet:
https://docs.google.com/spreadsheets/d/1FRP0FTDhoeJU0Q-4GxR06nYv2NY6xyo6KoZoP81ARHA/edit?usp=sharing

I need to create formulae for Columns E and G.

Under my table, I've made some notes and what I need to do.

 

[p_s]

Just to be clear:
Column A has the names of items (different in each cell).
Column B has the number of items of Column A that are in "stock".
Column C has the unit price of each item in Column A
In Column H The user inputs is a string of text that is a combinations of numbers lower than or equal to column B and the text from Column B (can be more than 1 item)

1. I need a formula to subtract the numbers in the user string from column B to the corresponding Column A item (Column E)
2. Also, each user has a budget. We need to subtract the unit price for all the items in the user string from this value. (Column G)