Combining dissimilar data

[dwighttrumbower]

I'm trying to combine some data that is dissimilar at detail level but could be combined at a month. Below is a picture of the current model. 
Product sales is at a detail level and I can sum it up at a year/month level. The table SalesIncentiveHistoryTmp is loaded from excel and need to be subtracted from monthly totals based on sales rep and product.
I'm trying something like this in a column. Total lost on a good way to do this.

if( Product = 'productname',
[Sales YTD] - IncentiveAmount, [Sales YTD] - [Sales PY YTD])

Any suggestions would be helpful.

Thanks

[marcus_sommer]

Your association between the data-sets isn't sufficient because it's only on the SalesRep and not including the product and periods. This means you may combine these 3 fields in a key-field in both tables to get a valid connection.

Another possibility would be to concatenate both tables by adding an extra source field because it are mainly the same data - just the point of view is different.