Walkthrough for a form

[smeco]

if anyone feels like it, I'm asking for a 'walkthough'
i'm doing this because so far the most useful topics i've read were walkthrough which explain the 'big picture' rather than little isolated details


I have the following tables:

COSTS (ID, amount, description) - a list of costs
AREAS(ID, name) - a list of areas: eg Spain, France etc
MONTHS(ID, name) - a list of months
CONNECTIONS(ID, CostID, AreaID, MonthID, amount) - for each cost I give the relevant area and month; I need to specify the amount because it could be 60% in March-Spain and 40% in April-France, say

I'd like to make a form where I choose a cost, and a submask shows me how the cost has been distributed in areas and months
I'd like this form done so that:
1) I can insert, modify and delete costs and 'connections'
2) a messagebox should appear when not all of the cost has been distributed
3) when I start entering 'connections', it should automatically put as amount all of the remaining cost to assign
4) When distributing the cost, I'd like to be able to enter percentages as well as amounts

hope that's clear

thanks in advance
smeco