Issues Calculating Function

[jaymoore1756]

I have a  function that I want to bring to FM. It is a function that returns a check digit for a OCR line that will eventually print on specific notices. I have tested the function in SQL and it is functioning. the function has been added to the data base.
I have three layers in FM an I have added it to the Database layers using the following line dbo.CPU_CheckDigit(UM00200.ACCOUNT_NO) as Check_Digit. I defaulted the account number for the calc so it would validate. So the issue is this ..
The check digit is calculated with the following 1) Doc ID = R222  2) Account # 3) Amount 4) Padding = 0000000000 5) and then the check digit. Several things a)Doc ID and padding do not exist in the database so I created columns for them in FM. b)Account number and account and amount are numeric so I will  have to cast or convert them.

So the issue is how do I set up the formula in FM so the check digit calculates with the following (1,2,3,4 from paragraph 1)
dbo.CPU_CheckDigit(1,2,3,4 from paragraph 1)  as Check_Digit

Attempt to create the formula have failed getting many different errors (i.e. FM does not recognize the created column)
Thanks any help is appreciated