Select Item On Sheet A Automatically Paste Info To Sheet B

I have a workbook with a Cost Analysis sheet, a master menu sheet, and then all the sub sheets. I have coded command buttons on the master sheet, so once a category is selected, it goes to the appropriate sub sheet. On the subsheet is a list of items of varying sizes, and command buttons beside that which will allow the user to "Select" that particular size. Once the size is selected, the verbage in cell B5 plus the verbage (size) beside the selected amount, and the prices (labor and materials) in the next two columns, need to be transferred to the first available blank line, starting with line C5, to the Cost Analysis sheet. I have never done coding before for a Loop (i.e. For i = ???) and am not sure how to get it to do what I want. After they select that, they can pick a command button that takes them back to the master menu so they can continue picking various items until they are through. Then the Cost Analysis sheet will show all the items they picked, (name of item, material cost and labor cost: Columns B, C, & D). Not everything is coded yet (such as selecting a command button to go back to the main menu, because I wanted to make sure I could solve this problem before doing the easy stuff).

I read over quite a few of the previous threads and am not sure how to change them to suit my circumstance. I know some code (VB), but not much. I do not understand the concept of DIM, and how the loop works to make it happen myself, and all the websites I could find were not suited to my situation of copying three cells of data to the first blank cell on another sheet.