Is there a Goal Seek function in VB? Please help with mathematical problem.

I'm making an application that need to use a function like 'goal seek' in Excel. Here's the problem example:

Price: 100.000
Down Payment: 20% -> 20.000
Payment per month: 8.000 (assume a 10 month period)
Total Down Payment: 28.000 (20% of 100.000 + 8.000 first payment)

Now I want the Total Down Payment to be 30.000, so I need to change the Down Payment of 20% to another value. In Excel, I can use the Goal Seek Function to do this very easily, and the Down Payment results in 22,2222%.

How do I do it in VB?

Thanks.

I just solved it as a math equation and rearranged the values around (I wrote it using letters so i can get the required formula)

DownPayment = (MonthPeriod x TotalDownPayment - Price) / (9 x MonthPeriod)

Hi Andrew G, thank you very much for your solution, you're a genius! I really don't know how you can get that equation. Can I ask you for another solution? I need to add another variable to the problem:

Price: 100.000
Down Payment: 20% -> 20.000
Interest rate: 10% -> 8.000 (10% of 100.000 - 20.000)
Month period = 10 month
Payment per month: 8.800 -> (80.000 + 8.000) / 10
Total Down Payment: 28.800 (20% of 100.000 + 8.800 first payment)

Again, I want the Total Down Payment to be 30.000, and using the goal seek function in Excel, the Down Payment should be 21,3483146067416% (21,3484%)

Thank you very much Andrew.

This one is a tad more longer :p

DownPayment = (TotalDownPayment x Month - Price(1 + IR)) / (M - (1 + IR))

IR = 0.1 (10/100) ;)

Or written condensed :)
Attachment 55973

Thank you very much Andrew G! You are truly a genius! :wave:
I really can't figure out how you can come out to the equation, I have tried hard :blush:

thanks again!

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Thank you. :)