マクロ関数定義するならこんな感じかな

Function ConcatRange(oData) As String
Dim sRet As String
For i = 1 to UBound(oData, 1) step 1
For j = 1 to UBound(oData, 2) step 1
sRet = sRet & CStr(oData(i, j))
Next
next
ConcatRange = sRet
end Function