Hi @chrisccorbett. Just some process thoughts...
If you only want the Excel data to effect the drawing, and not the model it is referencing, then what I would do is allow the drawing's title block text boxes to be pointing to the drawing's own iProperties, then use an iLogic routine that will pull data from the Excel sheet, and set that data as the value(s) of the drawing's iProperties. Then just do a Sheet.Update, and/or DrawingDocument.Update to make the title block data update to show the new iProperty values. The above process would be much simpler/easier than using 'static' text in the title block, and trying to dig down into the title block definition's sketch and loop TextBoxes, trying to find the right ones to change the values to the right corresponding values.
How are your drawings' title blocks currently set-up...with static values, pointing to model iProperties, pointing to drawing iProperties, or something else?
Wesley Crihfield

(Not an Autodesk Employee)