I need some help on a formula for a heatmap and I'm hoping you clever people can assist me please;

I have two columns that hold a start date and an end date, (example below) and I want to show how many pieces of work are active in a given month.

Start Date End Date
01/01/20 01/11/20

So, I have been able to display that the work STARTS in January by using the below formula;

=COUNTIFS('Change initiatives'!$C:$C, C3, 'Change initiatives'!BB:BB, $D$2)

However, this only shows the start date, not the fact this piece of work runs from Jan 2020 - Nov 2020, which means my heatmap only shows work in Jan 2020 and not the remaining months up until Nov 2020

Can anyone suggest a revision/new formula that will help me show the ongoing nature of the work please????

Thank you!