In a nutshell, I am tackling an issue beyond my skills and but thought s-controls would work but I don't know how to write them. It is not necessary that it be an s-control. Anything that would work would be great.

Please note that the custom object Target is the child in the master-detail relationship with Account. I wanted the Install to be linked to the Target but found that this was not possible, so I thought I could pull in the target summary name from the Target to tie it all together.

Here is the example:Account: Bob's burger Shack

1. Custom Object: Install
2. Target Summary Name: I want to pull in the exact one above - please note that there may be multiple targets (past & present) but I only want to link it to one specific one
3. Installed Units: 1
4. Annual VPO: Once the correct target summary name is found(selected), then I want to pull in the Annual VPO field that is tied to it.
5. Daily VPO: Non-visible field to calculate the Annual VPO into a daily VPO
6. Gallons gained: This will be a field that calculates (the daily VPO* # of days remaining in year) * the number of installed units

 Can anyone help? I am stuck on the red highlights. Other solutions/ ideas would be interested in as well. I greatly appeciate time & efforts in advance. Needless to say, I have zero programming skills.