Dragging Indirect Formula Down

Hello,

I am looking to copy/drag down the following formula (which is housed in C77):

=COUNTIF(E77:(INDIRECT($C$75&77)),1)/COUNT(E77:(INDIRECT($C$75&77)))

Example for each row:
=COUNTIF(E77:(INDIRECT($C$75&77)),1)/COUNT(E77:(INDIRECT($C$75&77)))
=COUNTIF(E77:(INDIRECT($C$75&78)),1)/COUNT(E77:(INDIRECT($C$75&78)))
=COUNTIF(E77:(INDIRECT($C$75&79)),1)/COUNT(E77:(INDIRECT($C$75&79)))
etc..

The intended result is that I would like to be able to specify a specific Column as part of C75 (lets say "G") and have that apply to all of the respective rows, but first I need to populate each row with this formula so that it applies. The problem is that when I try to drag/copy down the formula, "77" remains unchanged (would expect it to increase with each row: 77, 78, 79, etc).

Any help or recommendations are greatly appreciated!