yes, you can create Gant charts in Excel, with Conditional Formatting.
I found it in the Tips section of this website a while back.
For example, the formulas could be:
(when using all 3 conditions)
Condition 1 - Formula Is =D$1=$B2
Format a bordered box, except on the rightside
Condition 2 - Formula Is =D$1=$C2
Format a bordered box, except on the leftside
Condition 3 - Formula Is =AND(D$1>$B2,D$1<$C2
Format a bordered box, all the way around
When you have consecutive data in Row 1,
Min data in Column B, & Max data in Column C.