update value and edit items already update on sheet by userform

Hi,
I have work on my first VBA on the attached file. I need help in couple of them. First let me tell what the sheet is all about. I have a sheet on as Item master list that has all the items used in cooking. along with price and broken down to per gram or per ml. the rest of the sheet is the menu costing sheet where items are updated using userform. Now what i want is that in the attached sheet example say on the sheet 1 the value update for "egg" is one dozen ( 12 peice ) Rs.60, which bring the value of 1 egg to Rs.5. Now what i want is if for some reason the egg price should or have gone up say Rs.80 ( 12 peice) so the value for a single has gone up by Rs.6.67. And since there are close to 45-50 sheets where eggs are used its not possible to update every sheet. what code to write so that when i update the value Rs.80 on sheet1 the result for a single peice is reflected on all the sheet where eggs are used.
Second i also want say in sheet 2 named egg nog milk used is 80 ml but that has to be 100ml. which needs to be corrected. how or what is to be added in the userform so that i can edit the information which out disturbing any other info, and also can be use in any of the sheet to correct such info.

Thanks in advance