Pattern p = Pattern.compile("\\b(?:Input|Calc)![A-Z]\\d+\\b");

1. (?:Input|Calc) — either keyword

2. ! — the literal exclamation that both forms share

3. [A-Z] — exactly one uppercase column letter

4. \\d+ — one or more digits

5. \\b — word boundaries so you don’t bleed into adjacent text

Quick test with your samples

Matches found:

• ADD(Input!A34 + Calc!D93) → Input!A34, Calc!D93

• Input!D343 = 1000 → Input!D343

• Calc!D71=IF(HasValue(Input!D4), "…") → Calc!D71, Input!D4