Adding data validation text to another occupied cell

[baggypants]

Hello, I am hoping to find a way to track projects through different workstations. I have several different shops and using data valadation I am using a drop down box to show where the project currently is. What I need to do though is as each station selects on its arrival, the data needs to move to another cell, adding the new text.
For example a unit may need to flow through ins/assy/painting. As "ins" is first selected the text should go to a cell. Then "Assy" will be selected. That cell should then read "ins/assy".....ans so forth. Untill finally we have ins/assy/painting.
I hope this makes sense.
Thank-you!!