[XLjedi]

Yes, I do that all the time. You need to use the Unit Advance tool on the unit popup menu.

Note: this assumes you have the proper settings for scale already set in MoBo

1) Plot a contact on the 0100 location of the unit by hovering cursor over unit location and pressing the C key.

2) Hover over the new contact and press V to enter a speed/heading vector for the unit. You can make an educated guess usually based on some amount of known information, moving slow heading SE for example.

3) Enter a time for the contact by hovering over the unit and pressing T. MoBo accepts several different time formats, you can enter 0100 if you like.

4) Right-click the contact and select Advance. This will allow you to reposition the unit based on any time in the future or past. You can enter the time in the textbox or use the slider. When you're happy with the new location of the unit just press OK. In your case, you would either enter 0400 in the textbox or use the slider to adjust the unit position for 0400.

Yes, the unit Data entry area for time is storing the same information as hovering over the unit and pressing T to enter the time, it's just faster to use the T key for a quick time entry.
Sometimes I like to see where the unit is at various times in the past/future. You can use the "Plot Node" feature on the Unit Advance dialog window to plot nodes anywhere along the timeline. The advance tool is only as good as your speed/hdg estimate. When in doubt go with a higher guess on speed and you'll at least be pretty well assured that you'll arrive at the intercept point ahead of the target.