Limiting multiple scroll bar selections to total a maximum calculated amount

Hello: I've attached a spreadsheet to show you what I have so far. I'm wondering if anyone has done this before or can get me started with a good idea. I'm guessing this will require a macro and/or active X control vs. the simple format I have now. Currently we have 3 sets of scroll bars with each set having 6 criteria to choose from and based on the selection it calculates a total cost. Now we want to "limit" the selection if the max is reached. So for example if the user selects a combo of stuff that exceeds $20,000, is there a way to force the sliders to correct back to a number that totals $20K. So for example if the user reaches a total that is $23K, then the program either reverses the last selection or even better would be it can look at the $3K variance and then adjust something down based on that value using the Base Costs in the table. This idea is too complicated to wrap my head around.

I'm not sure if this is do-able even so I may just have to settle for an "alert" to show up (which is easy to do) but thought I'd ask the creative minds in here before just tossing the idea. If it's not possible that is okay too.

For my spreadsheet I have 2 tabs. One is the sliders and the other has the data used for the sliders.

TIA!

P.S. I've already scoured the forum but was unable to find an answer to this. If there is something along these lines - even to get me started, please let me know.