Nevermind, found the solution:
Based on a filled Dimension-table:
1) Substract all records from your source which won't appear in your dimension table (select distinct ..where not in..). This is going to be the new dimension table data.
2) Use a proc append (or whatever you want) to append your current dimension table.
3) Give the dimension table new id's, even if they already exist. The data shouldn't be rearranged or sorted, so this way the fact table still refers to the same dimension data.
However, there should be a better way, cause my way seems to be tricky (you really want to avoid your data from being changed, especially for a complete dataset/dimension table in a starschema)
I'm still open for new ideas, bring them on!
Ps. using the id based on '-' separated key will work better for me!