Invoking Function error

Invoking Function error

Hi all,

I can't figure out why I'm getting an error.

I'm trying to Create a field in Form2 when a record is successfully created in Form 1.  I want the new record in Form 2 to be identical to the one in Form 1 apart from field, Amount, being increased by 50%.

I have defined the following Function:

AMR = (input.Amount * 1.5) ; 
return AMR;

which works when I test it by executing it.

Then, in Form 1 workflow, I have chosen Insert Record in the Add On > On Success Tab

In each category, I have simply typed input.<CategoryName>, but in the Amount field, I have tried to invoke the above function through the GUI by going to User Defined Functions, selecting the above function which appears as:

property_transactions_v1_0.Calculations.AMC_R(<Amount>)

Which I then change to 

property_transactions_v1_0.Calculations.AMC_R(input.Amount)

But I keep getting a "Null" error when I click Done.

Can anyone let me know what I'm doing wrong?