separate characters from numbers in cell reference

I have a cell reference that is read in from a worksheet

It is read in as a string ex. "D3:D2600"

I need code to calculate how many entries are in that range (2598)

Unless there is another easier way, I will split the string based on the semicolon, then remove the letter from the numbers, and subtract the numbers.

Does anyone have code that can quickly strip the characters (Column A to IV) from the rows?