Projected coordinate system and coordinates

I've been trying to get latitude and longitude to work with our projected coordinate system of NAD_1983_HARN_Transverse_Mercator but the decimal degrees do appear to be registering as decimal degrees, but as meters from the origin coordinates. I've tried configuring the WKID entries but nothing seems to make any difference. The only way I can get the points in the right location is to use a map source that doesn't use a projected coordinate system. The problem with that, of course, is the outline of the state (Wisconsin) doesn't look "right". Can a latitude/longitude from a data linked Excel file be projected?