A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
Sheet 2 with the in and out will need to include the starting inventory point as "In" figures in order for a formula to include them and then calculate additional In/Out changes. Here is my sample of your Sheet 2. Starting inventory is highlighted in yellow.
On Sheet 1 you can then use this formula to calculate the inventory and keep a running total of that inventory based on additions to the In/Out columns in Sheet 2. It is entered in B2 and filled down for all Items.
Note that the Units, kg or tanks, must be separated from the numbers for Excel to treat the inventory and change numbers as numbers and be able to calculate the running totals.
=SUMIF(Sheet2!$A:$A,A2,Sheet2!$B:$B)-SUMIF(Sheet2!$A:$A,A2,Sheet2!$C:$C)