Improve performance getting or setting values in cells through VBA - vba

Question

I've managed to connect to a web service and retrieve data to finally insert it into a sheet.
Looks like when I perform this final operation, the sheet gets the focus and the screen blinks constantly until this ends, which is a little awkward for the user and it depletes performance. We are talking that inserting about 1000 rows with 4 different parsed columns lasts for about 5 seconds.
Is there a way to do this "on the background"? I noted that basically "every action" I performed (like reading values or setting them) requests the focus on that concrete sheet, so I basically return the focus to the sheet who called the procedure once everything ended.
My code is the following:
For i = 3 To UBound(Data) - 1
If (IsNullOrWhiteSpace(Data(i))) Then
Exit Sub
End If
splitted = Split(Data(i), ";")
For j = 0 To UBound(splitted)
Cells(i - 1, j + 1).Value = splitted(j)
Next
Next
Many thanks, I'm new into this VBA world.

Answer 1

for starter, place:
Application.Calculation = xlCalculationManual
at the beginning of your Sub and:
Application.Calculation =xlCalculationAutomatic
right before End Sub
then let's see further three steps to speed things up:
a first step could be replacing:
For j = 0 To UBound(splitted)
Cells(i - 1, j + 1).Value = splitted(j)
Next
with:
Cells(i - 1, 1).Resize(, UBound(splitted) + 1).Value = Application.Transpose(Application.Transpose(splitted))
so that you write a whole row in one shot
a second step could be working with arrays and write the content of a 2D array in one shot:
Dim Data As Variant
Dim nRows As Long, nCols As Long, i As Long, j As Long
' >>>> here your code code to fill 'Data' variant array <<<<
ReDim notNullData(1 To UBound(Data) - 3) As Variant '<--| size 'notNullData' 1D Variant array to the maximum possible rows
For i = 3 To UBound(Data) - 1
If IsNullOrWhiteSpace(Data(i)) Then Exit For '<--| exit loop at the first null or empty 'Data' value
nRows = nRows + 1 '<--| update valid rows counter
notNullData(nRows) = Split(Data(i), ";") '<--| fill 'notNullData' array with an array from current 'Data' row content
If UBound(notNullData(nRows)) > nCols Then nCols = UBound(notNullData(nRows)) '<--| update maximum n° of columns to be written
Next
ReDim dataToWrite(1 To nRows, 1 To nCols + 1) As Variant '<--| size 'dataToWrite' 2D Variant array to 'Data' array valid rows number and calculated maximum nr of columns
'fill 2D 'dataToWrite' array processing 'notNullData' 1D array
For i = 1 To nRows
For j = 0 To UBound(notNullData(i))
dataToWrite(i, j + 1) = notNullData(i)(j)
Next
Next
'write 2D 'dataToWrite' array in one shoit
Cells(1, 1).Resize(nRows, nCols + 1).Value = dataToWrite
a third step would involve IsNullOrWhiteSpace() function