Pre-populate a field based on another field in an edit form

[ShadowTech]

Hello,

I'm looking to have field "A" populated with data from a SQL table when inputting a number in field "B". I'm working with two different data sources here. The main data source is a SharePoint list where the data from the Edit form will end up but pulling in data from the SQL table.

The formula works fine if I switch the mode to "New" but for what ever reason the "Edit" mode throws back an error.

If(
    EditForm.Mode = Edit,
    LookUp(
        SQLTable,
        SONumber = DataCardValue45.Text,
        TotalValue
    ),
    ThisItem.'Total Value'
)

Any suggestions on how to make this work?

Thanks in advance.

[zmorek]

Try

If(
    EditForm.Mode = FormMode.Edit,

Also with the below, are you comparing a number column to a text field? 

SONumber = DataCardValue45.Text,

[ShadowTech]

@zmorek  To question (2), Yes. The SharePoint Field (ThisItem.'Total Value') is a currency field. How can I convert that?