You can't really mix formulae & constants without interjecting some VBA.
I would thus suggest either moving the in-cell formula notification to an adjacent cell or modifying the DV rule such that it permits only a valid date when your existing IF is satisfied, e.g:
the above simply states that M61 entry must be within the last 30 days and that none of B61:D61 are Blank/Null.
It should be noted that the Validation rule is only ever applied at point of entry. For ex. were B61:D61 non-blank and M61 assigned a valid date and the user then deletes content of B61 this would not force M61 to then flag as invalid.
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