Mapping one account with two sales rep

Alright, so you make a new column in fact table called rep key. The DAX formula looks like this:

Repkey = 'Fact1 Table'[Code]&" "&'Fact1 Table'[Sales rep]

You make a similar column in your rep table:

Repkey = 'Rep Table'[code]&" "&'Rep Table'[Sales rep]

Then you create a relationship between fact table and rep table with these columns.

Then you create a calculated column with this DAX formula:

Total amount = 'Fact1 Table'[Amount] * RELATED('Rep Table'[Split])

Let me know how it goes. I'll gladly elaborate.