In VBA how do I store a lookup value in an array, then loop thru the array

Attached I have a 3 tab spreadsheet: Source, Today, and Not Matched
1.In VBA I would like to compare the Today tab with the Source tab based on fields "Amt" "Store" and "Date"
2.If I find a match I would like to store the "ID" value from the source tab for the first match found (note there could be multiple matches)
3.I would then like to re-loop thru the Source tab to find any ID's that are not found in the stored value from above
4.The final step would be I would write out the missing ID's to a tab called "Not Matched"

I am familiar with looping, but I do not know the approach or syntax to create an array for the id and to store the array....
ee-Not-Matched.xlsx